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Household Chemistry 



FOR THE USE OF 



STUDENTS IN HOUSEHOLD ARTS 



BY 



HERMANN T!^ VULTE. Ph.D., F.CS. 

Assistant Professor of Household Chemistry in 
Teachers College, Columbia University 



E ASTON, PA. 

THE CHEMICAL PUBLISHING COMPANY 
1917 



<ri 



\V1 



Copyright, 1917, by H. T. Vulte. 



JUL 16 1917 



©a." 467865 



PREFACE. 

This book is presented for the general study of the 
subject of chemical operations in the household. It is 
designed to meet the needs of secondary schools and 
colleges. For the former purpose, the instructor will 
find it possible to make such selection of material as will 
cover the field of work broadly in a semester. A 
thorough completion of the course indicated in the book 
would require the attention of the college student for one 
year. It is highly advisable in this longer course that 
one-third of the period be given to explanation and 
discussion of the topics in the form of lectures. In 
the shorter course the object may be accomplished by the 
more informal conference system. 

It has seemed best to include a large amount of de- 
scriptive matter in this book, which was not a feature of 
former editions. 

I wish to express my great indebtedness to my as- 
sistants, Mrs. Ellen Beers McGowan and Miss Sadie B. 
Vanderbilt, for valuable assistance and advice in the prep- 
aration of this volume. 

H. T. V. 

May, 1915. 



TABLE OF CONTENTS. 



CHAPTER I. ^ 
Introductory. page 

Outline of Course in Organic Chemistry i 

CHAPTER II. 
Atmosphere and Ventii^ation. 
Composition of the Air. Properties and Uses of Constitu- 
ents. Experiments. Factors in Ventilation ; Methods of 7 

CHAPTER III. 

Water. 
Physical and Chemical Properties. Classification of Drink- 
ing Waters. Qualitative Examination. Purification of 
Water. Hard and Soft Water. Experiments 23 

CHAPTER IV. 

Metals. 
Metals and Alloys. Processes of Manufacture. Physical 
and Chemical Properties. Effect of Acids and Alkalies. 
Methods of Cleaning, Experiments 43 

CHAPTER V. 
Gi^ass, Pottery, and Porcelain. 

Manufacture. Properties. Experiments 62 

CHAPTER VI. 

FuEES. 
Classification. Solid Fuels: Nature and Properties. Liquid 
Fuels : Manufacture, Nature and Properties. Gases : 

Manufacture, Properties. Experiments 67 

CHAPTER VII. 
Carbohydrates. 
Classification. General Properties. Glucose. Fructose. 
Galactose. Sucrose. Maltose. Lactose. Starch. Dex- 
trin. Glycogen. Celluloses. Experiments and Practical 
Applications 88 



CONTENTS V 

CHAPTER VIII. 
Fruits and Fruit Juices. page 
Composition. Analysis of a Fruit. Experiments in Jelly- 
Making 123 

CHAPTER IX. 
Fats. 
Formation and Occurrence. Properties. Experiments. 
Butter ; Specific Tests 129 

. CHAPTER X. 
Proteins. 
Classification. Occurrence. Solubilities. General and 
Specific Properties. Hydrolysis. Albumins and Globu- 
lins. Egg. Gelatin. Bone. Muscle. Beef Extracts. 
Milk. Cheese. Experiments 141 

CHAPTER XI. 

Baking Powders. 

Composition. Comparison and Types. Experiments 170 

CHAPTER XII. 
Tea, Coeeee, Chocoeate and Cocoa. 
Sources. Constituents. Methods of Preparation. Experi- 
ments 176 

CHAPTER XIII. 

Ferments and Preservatives. 
Yeast. Lactic Acid. Acetic Acid. Butyric Acid. Experi- 
ments. Method of Food Preservation. Tests for Pre- 
servatives. Tests for Purity of Certain Foods 183 

CHAPTER XIV. 

Disinfectants and Disinfection. 
Physical and Chemical Methods of Disinfection. Antiseptics. 
Tests for Disinfectants I9S 



VI CONTENTS 

CHAPTER XV. 

Cleansing Agents. page 

Classification, Soaps and Soap Powders. Manufacture of 
Soap. Soap Analysis. Scouring Powders. Metal Pol- 
ishes. Tests for Cleaning Agents. Bleaches, Grease and 
Stain Removers. Bluings. Experiments 201 

CHAPTER XVI. 

VoivUMETRIC AND GRAVIMETRIC ANALYSIS. 

Normal Solutions. Preparation of Solutions. Use of Indi- 
cators. Analysis of Vinegar, Cream of Tartar, Baking 
Soda, Household Ammonia. Analysis of Soap or Soap 
Powders. Cereal Analysis. Kjeldahl Determination of 
Nitrogen, Estimation of Reducing Sugar 215 

CHAPTER XVII. 
Reagents. 

Methods of Preparation 229 

APPENDIX. 
Useful Tables. List of Apparatus 234 



CHAPTER I. 



INTRODUCTORY. 

Courses of instruction in Household Economics group 
themselves principally about foods or other materials 
used in the household, most of which are of so-called 
organic origin. Hence some fundamental instruction in 
the nature of organic compounds is necessary, and pref- 
erably should precede a course in household chemistry, 
which is largely an applied chemistry of the carbon com- 
pounds. Often, however, a preliminary course in organic 
chemistry cannot be introduced into the curriculum. 
For that reason, an outline of a series of lessons in the 
chemistry of the carbon compounds is given here, de- 
signed to be presented as lectures and experiments run- 
ning parallel with the work in household chemistry and 
often merging into it. In such a combined course, the 
outline as given will need to be adapted to the allowed 
time, perhaps to the exclusion of the aromatic com- 
pounds, and it may be necessary to perform many of the 
experiments as demonstrations. To give the study its 
proper emphasis and value, stress should be placed less 
upon individual than upon type compounds, and upon 
their interrelation and properties, always with a view 
to enriching and making more effective the practical 
knowledge which the student has of substances met in 
everyday life. 

It may be pointed out, in addition, that a recent course 
in general chemistry of the most modern type should be 
required as a prerequisite of household chemistry. In 



2 HOUSEHOLD CHEMISTRY 

such a course the subject matter should be so selected 
that the material handled hi household chemistry shall 
not be entirely unfamiliar. For example, more definite 
information would be useful with regard to the consti- 
tution and properties of the important metallic elements, 
and a few of their simpler compounds. 

Outline of Course in Organic Chemistry. 

I. Originai, and Present Meaning oj? Term ''Or- 

ganic/' 
Importance of organic chemistry — Some differences 
between organic and inorganic compounds — Organic 
chemistry the chemistry of carbon compounds — The car- 
bon atom; its valency; graphic expression of valency; 
tendency to combine with hydrogen. 

II. Chain Hydrocarbons. 

The Methane, Ethylene, and Acetylene Series. 

Development of Series — Nomenclature — Common for- 
mulae and differential — Properties — Occurrence of im- 
portant members. 

Application to Gaseous and Liquid Fuels. 

Experiments: Preparation of Methane, Ethylene and 
Acetylene. 

Reaction for the double bond. 

III. Isomerism Applied to the Hydrocarbons. 
Nature and effect of isomerism. 

IV. Saturation and Unsaturation. 

Meaning of — General formation of substitution and 



HOUSEHOLD CHE:MISTRY 3 

addition products — Isomeric forms — Formation of 
iodoform and chloroform. 

Experiment: Preparation of iodoform. 

V. Al.C0H0I,S. 

Derivation from the hydrocarbon through substitu- 
tion^ — relation to metaUic hydroxides — Nomenclature — 
General physical and chemical properties and reactions — 
Source and uses of important alcohols — Isomeric forms ; 
primary, secondary , and tertiary alcohols — Unsaturated 
alcohols — Glycols and polyhydric alcohols — Sulphur 
alcohols or mercaptans. 

Application to liquid fuels; to carbohydrates; to fats; 
to fermentation; preservation of foods. 

Experiment : Preparation of ethyl alcohol. 

Detection of methyl alcohol. 

VI. Al^DKHYDES AND KETONE^S. 

Formation from alcohols — Comparative properties and 
reactions — Name, source, and uses of important ex- 
amples. 

Application to carbohydrates; preservatives; flavoring 
extracts. 

Experiments : Preparation of formaldehyde, acetalde- 
hyde and acetone. 

Reduction by aldehydes, such as the Fehling's reac- 
tion. 

VII. Fatty Acids. 

Formation from aldehydes — Nomenclature — General 
properties and reactions — Occurrence and properties of 



4 HOUSEHOIvD CHEMISTRY 

important examples — Unsaturated acids : occurrence and 
characteristics. 

Application to fats and oils. 

Experiment : Preparation of acetic acid. 

Separation of a fatty acid from a fat. 

Illustration of drying and non-drying property. 

VIII. Schematic Review of Interrelation. 

Hydrocarbon «•-> Substitution or Addition «»-► 
Alcohol "-♦ Aldehyde «•--»► Acid 

IX. Esters. 

Formation of type esters reviewed — Waxes — Glyceryl 
esters of fatty acids : general properties ; occurrence and 
properties of important fats and oils. 

Application to fats and oils. 

Experiment: Decomposition of a fat. 
. Preparation of ethyl acetate. 

X. Ethers. 

Formation — Analogy to metallic oxides — Nomencla- 
ture — Important examples — Properties — Relation of 
ethers to alcohols; of thio ethers to mercaptans. 

Application : Ether extraction processes. 

XL Oxidation Products oe Gi.ycoi.s and Poi^yhydric 

AlvCOHOLS. 

Hydroxyacids — Dicarboxylic acids — Special examples : 
Glycollic, lactic, sarcolactic, oxalic, succinic, malic, tar- 
taric, citric, aconitic — Sources and properties. 

Application to milk; to muscle; to fruits and fruit 
juices. 



HOUSEHOLD CHEMISTRY 5 

XII. Nitrogen Compounds. 

1. Alky I Cyanides. 

Analogy to halogen derivatives — Hydrolysis of 
cyanides — Other cyanogen compounds : properties and 
uses of — Prussian blue as bluing. 

2. Amines. 

Primary, secondary and tertiary amines — Quaternary 
ammonium bases — Unsaturated amines and related com- 
pounds — Important examples. 

3. Amides. 

Structure and properties — Amides of dicarboxylic 
acids — Important examples. 

4. Amino Acids. 

Formation — Nomenclature — Properties and reactions 
Important examples — Synthesis to peptids — Relation to 
proteins. 

5. Proteins. 

General composition, properties, etc. 

6. Purin Group. 

Purin ring and substituted purins — Adenin, guanin, 
hypoxanthin, xanthin and uric acid; caffein.; theo- 
bromine. — Pyrimidin base. — Relation to nucleoproteins. 

XIII. Aromatic Compounds. 

Benzene ring — Homologues — Benzene, naphthalene 
and anthracene : source and importance — Benzene deriva- 
tives analogous to those of the straight chain series — 
Formation of substitution products; phenols; alcohols; 
aldehydes; acids; amino compounds; diazo compounds; 



6 HOUSEHOLD CHEMISTRY 

leuco compounds — Properties and commercial importance 
of compounds — Dyes. 

Experiments: Preparation and detection of benzalde- 
hyde and of benzoic acid. 

Detection of vanillin and saccharin and salicylic acid. 

Preparation of aniline. 

Diazotizing aniline. 

Coupling diazos and phenols. 

Formation of leuco compounds. 

Reduction of indigo blue and subsequent oxidation. 

Preparation of helianthin and eosin. 



CHAPTER II. 



ATMOSPHERE AND VENTHATION. 

Probably no subject so important to life as the air we 
breathe is so little understood, nor is there any other 
instance of so many evils arising from ignorance. A 
knowledge of the relation of pure air to health and ef- 
ficiency should be a part of the education of people in 
general. In no other way will there be a solution of 
problems of ventilation in homes and public buildings, 
or of sanitary housing in large cities, and the stamping 
out of devastating diseases. A fundamental knowledge 
of the properties and functions of the atmosphere, and 
the principles of ventilation, is therefore all-important 
for the student of household chemistry. 

Composition of the Air. — Pure air is not a compound 
of definite composition, but a mixture of gases. The 
two most important, oxygen and nitrogen, occur in the 
proportion of about 20 parts of the former to 79 of the 
latter. Other essential constituents are carbon dioxide, 
which in pure air averages in amount a little over 3 
parts in 10,000 or 0.03 per cent, to 0.04 per cent., and 
aqueous vapor. Traces of argon, krypton, neon, ozone, 
hydrogen, ammonia, nitrogen acids, nitrites and nitrates, 
helium, and several other substances are normally found 
in varying amounts. 

In addition to the above, there are always present in 
ordinary air many substances classed as impurities, the 
kind and amount varying with the locality. Dust from 



\J 



8 HOUSEHOLD CHEMISTRY 



the soil and from factory operations is found as sus- 
pended matter, together with micro-organisms, pollen, 
plant seeds, and soot. Offensive gases may contaminate 
the air of manufacturing centers, but they are usually 
more disagreeable than dangerous. The air of cities 
contains anywhere from loo to 5,cx)0 times the amount 
of dust and bacteria that is found in country air. 

Properties and Uses of Constituents. — Oxygen. — Oxy- 
gen is the life-supporting element for all animals and 
plants. Diluted as it is with nitrogen, the oxygen of 
the air is in the condition and proportion best adapted 
to sustain most forms of life. In materially increased 
amount it is a poison to human beings; on the other 
hand, life cannot exist if the proportion falls to four- 
fifths of the normal, or i6 per cent, instead of about 
20 per cent. 

In animal organisms, a relatively small amount of 
oxygen is concerned in the process of respiration. Of 
20.9 per cent, inhaled by human beings, 16 per cent, is 
returned in the exhaled air, together with about 4.4 per 
cent, of carbon dioxide. The oxygen used, however, in 
the respiratory exchange suffices to supply heat and 
energy to the body by means of oxidative processes in 
the protoplasm of tissue cells. 

Plants require oxygen for respiratory and other 
processes as animals do. Part of the necessary amount 
is inhaled; part is obtained in the process of photo- 
synthesis, through the action of chlorophyll and sun- 
light. A plant lacking in chlorophyll, such as a mush- 



HOUSEHOI^D CHEMISTRY 9 

room, absorbs oxygen directly from the air; green 
plants, in the presence of sunlight, build up carbohydrate 
material in their cells by synthesizing carbon dioxide 
and water, and in the operation release oxygen. The 
cells use as much of this as they require; the excess is 
returned to the air. It is estimated that an acre of 
woodland withdraws in one season about 4^ tons of 
carbon dioxide from the atmosphere, and returns 3^ 
tons of oxygen.^ In darkness the chlorophyll becomes 
inactive; the plant then takes oxygen from the air. It 
is probable that the roots absorb oxygen from the soil 
and from ground water. 

Ozone. — Ozone is a peculiar form of oxygen which 
exists as O3. It is produced from O^ by electrical 
discharge, by the action of moist air on phosphorus, or 
by several chemical reactions, such as the action of con- 
centrated sulphuric acid on potassium permanganate. 
Its odor is noticed around static electrical machines and 
during thunderstorms. Ozone is a powerful oxidizing 
agent, but is found only in minute quantities in ordinary 
air. The salubrity of the air in evergreen forests is 
ascribed to ozone, formed as a product of the slow oxi- 
dation of turpentine and similar plant products. 

Nitrogen. — Nitrogen is an inert gas ; it does not burn 
nor support combustion, and its chief value to organ- 
isms is in the form of compounds. It is not utilized in 
human respiration except as a diluent of oxygen. In 
the plant world certain species of bacteria such as the 

^Harrington: Practical Hygiene. 



10 HOUSEHOLD CHEMISTRY 

micro-organisms found in the root nodules of some 
legumes, carry nitrogen directly to the pea, bean or 
clover. How far other plants are able to utilize atmos- 
pheric nitrogen is a question. The main source of the 
organic nitrogen in their tissues is the nitrogen com- 
pounds in the soil due to micro-organisms, and ammonia 
and nitrates washed down by the rain. 

Carbon Dioxide. — Carbon dioxide is a heavy gas 
which will not support combustion or respiration. It is 
the result of oxidation processes, either in respiration, 
fermentation, the burning of tons of fuel, or chemical 
action in the soil. Harrington estimates that 
5,000,000,000 tons are discharged annually into the 
atmosphere. The amount of carbon dioxide in the air 
may vary from two parts in 10,000, or 0.02 per cent, in 
the purest air to 30, 40 or even 100 parts in bad con- 
ditions of overcrowding. Only in greater amount, how- 
ever, such as was found in the Black Hole of Calcutta, 
is it destructive to animal life. Undiluted, it causes in- 
stant suffocation by spasmodically closing the glottis. 

On account of the solubility of carbon dioxide in 
water, considerable amounts are taken out of the atmos- 
phere by rain and go to form carbonates in the soil or 
remain as carbon dioxide in the water. 

Aqueous Vapor. — The term aqueous vapor is mis- 
leading and does not strictly represent the gaseous form 
in which the water in question exists in the atmosphere. 
The amount of aqueous vapor which a given volume of 
air is capable of holding without condensation depends 



HOUSEHOIvD CHEMISTRY II 

Upon the temperature of the air. At o° C, a cubic meter 
of air is saturated if it contains 4.87 grams of moisture ; 
at 20° C. or 68° F. it can contain 17.157 grams, and at 
32° C. or about 90° F. it may hold 30 grams. It follows 
that a precipitation of moisture results when the tem- 
perature of vapor-laden air changes from a higher to a 
lower point. The temperature at which moisture is 
deposited is called the dew point. 

The rate of elimination of moisture from bodies de- 
pends largely on the amount of moisture already car- 
ried by the air. When air is saturated, it can take up no 
more; evaporation, therefore, cannot occur, and the 
moisture normally given off by the human body, for ex- 
ample, is deposited on the surface of the skin. This most 
disagreeable condition of stickiness is associated with 
days of great humidity in summer, with moist, raw days 
in winter, and with overheated crowded rooms. 

Humidity is measured in terms relative to the satura- 
tion point of the atmosphere at any given temperature. 
A relative humidity of 50 means that the air contains 
only 50 per cent, of its moisture-carrying capacity at that 
temperature. The limits of comfort are generally given 
as between 40 and 75 ; a humidity of 75 to 100 is op- 
pressive to man but beneficial to plants. 

The relation of atmospheric moisture to heat is most 
important. Water has a great capacity for heat and 
gives it up slowly. It acts therefore as an equalizer of 
the sun's heat and a moderator of temperature. In semi- 
arid and desert regions, where the air is moisture-free, 
2 



12 HOUSEHOLD CHEMISTRY 

and at high altitudes where the amount of vapor is 
relatively less, extreme heat during the day and a sudden 
fall of temperature at night are observed. It is esti- 
mated that the absorptive and radiative power of aqueous 
vapor is 16,000 times that posessed by air. 

Dust. — The relation of dust to aqueous vapor is sig- 
nificant. Without this suspended matter in the air there 
would be little or no precipitation of moisture, but a 
constant state of saturation would be possible. The 
particles act as nuclei round which vapor condenses as 
fog or rain. In large manufacturing cities the preva- 
lence of soot and dust in the air accounts for frequent 
fogs. Bacteria cling to dust particles and with them are 
washed out of the air by rain. 

General Properties of the Air. — Density. — The density 
of the atmosphere varies, the principal factor in varia- 
tion being altitude. At 3^ miles elevation it is only one- 
half as dense as air at sea level and therefore exerts one- 
half the pressure. The normal pressure of the atmos- 
phere at sea level upon each square inch of surface is 
about 15 pounds, but this pressure, which amounts to 
30,000 pounds on the average body, is not appreciated, 
since it is exerted equally in all directions. Air pressure 
is commonly measured by the height of the column of 
mercury which it is capable of supporting, the recording 
instrument being called a barometer. A normal pressure 
at sea level, exerted on the mercury at the base of the 
barometer tube, is sufficient to raise in the tube a column 
of mercury weighing 14.7 pounds. This is called a 
pressure of i atmosphere. 



HOUSEHOI.D CHEMISTRY 1 3 

When the mercury falls in the barometer, which us- 
ually happens before a storm, it is evident that atmos- 
pheric pressure has become less. This is because the 
air at such times probably contains more than a normal 
amount of water vapor, which is lighter than air, its 
density being 9, while air averages 14.5. The term 
heavy, sometimes used to describe the atmosphere in this 
connection, is contrary to fact. A further explanation 
of the barometric condition is found in the fact that as 
different portions of the earth's surface become un- 
equally heated, the warmer areas impart corresponding 
heat to their atmosphere. This causes a rising and 
dilation of air over a given section, the heated column 
overflowing at the top upon the cooler surrounding atmos- 
phere. Diminished pressure results in the rarefied 
column, with consequent expansion and a fall in tem- 
perature, until the moisture-precipitation point is reached, 
and the contained vapor of the air is condensed as 
cloud or rain. In changing from the vapor to the liquid 
form latent heat is released, which increases the rare- 
faction, and the upward movement and overflowing of 
the air column continue. Thus is created a condition of 
low pressure which the barometer indicates, while in 
the surrounding areas high barometric readings will be 
found. The rain area will naturally correspond with 
the area of low pressure. 

Diffusion. — By a fortunate provision of nature, gases 
of different specific gravities do not lie in strata when 
mixed, but diffuse until the mass is of uniform com- 
position throughout. If it were otherwise, a layer of 



14 HOUSEHOLD CHEMISTRY 

carbon dioxide, which is a heavy gas, would blanket the 
earth, and offensive and poisonous gaseous emanations 
would make most localities uninhabitable. As it is, all 
such gases diffuse through the atmosphere as soon as 
produced. Stratification of the air is not, however, en- 
tirely controlled by diffusion. The local movements of 
air currents caused by unequal heating operate like a 
motor fan and are a most potent equalizing influence. 

Heat Capacity. — Air has a considerable capacity for 
taking up heat, which is utilized in hot air heating. 

Liquid Air. — Air can be liquefied by causing it to 
escape slowly from tremendous pressure, so that much 
heat is absorbed in expansion. The temperature of 
liquid air is nearly 400° below zero Fahrenheit. In this 
state it volatilizes rapidly at room temperature, the more 
volatile nitrogen being given off first. This leaves an 
available source of oxygen, which is utilized in filling 
oxygen tanks. Liquid air has a faint blue color. 

EXPERIMENTS ON AIR. 

1. Presence of Oxygen — Pour an inch of alkaline pyrogallol 
into a short broad test tube, close with a rubber stopper, invert 
and mark the position of the stopper and liquid on a gum label 
pasted on the outside of the tube, shake the tube well, invert 
and open under water, mark the level of the water in the tube 
when open, and explain the phenomenon. 

2. Carbon Dioxide — Expose a few drops of lime-water or 
barium hydroxide on a slide to the air and notice that, by the 
end of the lesson, it is cloudy. What is the precipitate? Write 
the reaction. 



HOUSEHOI.D CHEMISTRY 1 5 

3. Hydrogen Sulphide — Moisten a filter-paper with a solution 
of acetate of lead and expose to the air until the end of the 
lesson. Notice the black coloration due to the formation of lead 
sulphide. This test works well in rooms where illuminating gas 
is used. 

4. Aqueous Vapor — Saturate a strip of paper with cobalt chlo- 
ride or iodide, thoroughly dry and expose to the air out and in 
doors; under moist conditions, it turns pink. 

Weigh a small watch-glass containing about i gram of fused 
calcium chloride, wait about 2 hours and weigh again. Note the 
increase in weight largely due to water. 

5. Dew Point — Take the temperature of the room, immerse 
the thermometer bulb in a glass of water, and add ice little by 
little until the first indication of moisture is seen on the outside 
of the glass. If humidity is low, add salt to hasten process. 
Note the thermometer reading; it is the dew point of the air in 
the room. 

6. Determination of Relative Humidity Use a sling or whirl 

psychrometer. This instrument has two thermometers fastened 
to a frame w^hich can be whirled in the hand. The bulb of one 
thermometer is covered with muslin which is made wet at the 
beginning of the test. As the instrument is whirled evaporation 
around this bulb reduces the recorded temperature until the dew 
point is about reached, that is, the temperature at which no 
further elimination of moisture takes place, but condensation 
occurs. When the wet bulb thermometer registers its lowest 
point the reading of both is taken and the dew point calculated. 
(See Glaisher's table. Harrington: Practical Hygiene.) 

7. Relation of Dust to Rain — Fit a 2-liter flask with a rubber 
stopper having 2 perforations. Pass 2 pieces of glass tubing 
through these, long enough to extend nearly half-way into the 
body of the flask. x\ttach pieces of rubber tubing fitted with 
pinch-cocks to the free ends of the glass tubing just above the 
stopper. Put in the flask sufficient water to a little more than 
fill the neck when the flask is closed and inverted. Keep the 



l6 HOUSEHOIvD CHEMISTRY 

flask inverted and allow the confined air to become saturated 
with aqueous vapor. Now withdraw some of the air in the 
flask by suction through one of the rubber tubes. The decreased 
pressure causes a fall in temperature and a condensation of 
moisture as haze or fine rain throughout the air space in the 
flask. At this point introduce air through the rubber tubing to 
restore the original pressure and the mist disappears. Now wash 
the air in the flask with the contained water until its dust content 
is removed. Repeat the experiment and note that no rain is 
produced in the dust-free air. 

8. Atmospheric Pressure — Pour 2 inches of water into a clean 
ordinary half-gallon can, boil vigorously and close the opening 
with a close-fitting cork. Remove the burner and when cool the 
can will collapse. The can should have a small opening and 
preferably be rectangular in shape. 

Ventilation. 

The scope of this book prevents a detailed discus- 
sion of ventilation and ventilatory systems. In fact it 
does not seem possible at present to make definite state- 
ments in regard to standards of temperature and composi- 
tion of air in a well-ventilated room, since the whole sub- 
ject of ventilation is undergoing revision. Experts dis- 
agree as to the comparative physiological effects of the 
constituents of vitiated air, and if perfect systems of ven- 
tilation have been devised, they are not in general use. 
However, until all buildings are equipped with such a 
system as a matter of course, a few facts and principles 
should be generally known and brought to bear on the 
ventilation of rooms under individual control. 

Effect of Heat and Humidity. — It has been well estab- 
lished that the main factors causing discomfort in 
poorly ventilated rooms are excessive heat and humidity. 



HOUSEHOIvD CHEMISTRY 1 7 

With increase in temperature, due perhaps to over- 
crowding, the moisture in the air increases proportion- 
ately toward saturation point. Evaporation from the 
body now becomes relatively impossible. But at a tem- 
perature of 70° F. or over, the body depends upon evap- 
oration of perspiration to maintain its heat equilibrium. 
The danger now arises that the checking of evaporation 
may cause the cutaneous blood vessels to become so 
congested that the temperature of the skin is raised and 
heat transfer by conduction and radiation is increased. 
This occurs at the expense of the efficiency of the other 
organs, particularly the brain. Headache, dizziness, and 
even fever may result. Relief is at once felt in such 
cases if evaporation is aided by setting in motion the air 
in the room. If this cannot be done by bringing in free 
currents of outside air, electric fans answer the purpose. 

On the other hand, too rapid evaporation of water 
from the skin and air passages will cause discomfort, 
This is felt in the dry air of steam-heated rooms. The 
skin becomes dry, the cutaneous nerves are irritated, 
and the effect is felt by the central nervous system. This 
trouble may be obviated by the evaporation of water 
from a dish placed on the radiator. 

The relation of heat and humidity to efficiency is 
clearly pointed out in an article on Work and Weather,^ 
by Dr. Ellsworth Huntington. The efficiency curves of 
over 500 wage earners in Connecticut were studied dur- 
ing a period of 4 successive years, and those of 1,600 

^Harper's Monthly Magazine, Jan., 1915. 



l8 HOUSEHOLD CHEMISTRY 

students at West Point and Annapolis for periods of 
2 and 6 years respectively. The declination in amount 
of work done is greatest at two periods of the year — 
through January and a part of February, when windows 
are kept closed and indoor conditions of temperature and 
humidity are below standard, and from the latter part 
of June to the end of August. In the summer of 191 1, 
part of which was the hottest in 100 years in the locality 
where the observations were made, the efficiency of the 
operatives dropped astonishingly; in 191 3, a cool sum- 
mer, there was very little lowering of the curve. 

Carbon Dioxide. — Contrary to former belief, carbon 
dioxide in the largest quantities likely to occur in the 
air of a room has little to do with the feeling of dis- 
comfort. If the room is kept cool, the increase may be 
up to 20, 30, or even 40 times the normal amount^ with- 
ojLit appreciable effect, and no serious physiological dis- 
turbance results until the carbon dioxide content is 
raised to about 3 per cent, with a corresponding lowering 
of the oxygen. This is approximately 75 times the 
amount present in pure air. At this point Dr. Angus 
Smith found feebleness of circulation, slowing of heart 
action, and quickened respiration, but could detect no in- 
convenience with 2 per cent. Pettenkofer and Voit ex- 
perienced no discomfort after long exposure to air con- 
taining I per cent, of carbon dioxide.^ 

An adult will add 0.6 cubic foot of carbon dioxide to 

^ Rideal : Report on Hygienic Vakie of Gas and Electric Light- 
ing, presented before Royal Sanitary Institute, London, 1907. 
^Education, London, Feb., 1912. 



HOUSEHOLD CHEMISTRY I9 

the air in i hour. Therefore in a room containing 3,000 
cubic feet, the carbon dioxide will increase in that time 
0.2 cubic foot per 1,000, or 0.2 part per 10,000, i. e., 
from an initial amount for pure air of 0.04 per cent., 
to 0.06 per cent., which is the limit of the standard of 
purity generally given. Theoretically the air of such a 
room with one occupant would require renewing each 
hour, but fortunately the average room, not being air- 
tight, is constantly receiving some outside air through 
various openings. 

"Crowd Poisoning." — Dr. Rideal states that the worst 
that can be said of even respiratory carbon dioxide is 
that it is often found in bad company. Emanations 
of a poisonous nature given off in breathing, cause the 
unpleasant odors noticeable to a person coming into an 
occupied room from the outside air. Disease germs are 
likely to be present, and to circulate more freely if dust 
is in the air. Moreover, sharp particles of dust may 
have an irritating or lacerating effect on eyes, nose, or 
lungs, making the tissues more susceptible to the entrance 
of bacilli. Tuberculosis is commonly spread in this way. 

Experiments made under the direction of C. E. A. 
Winslow, chairman of the New York State Commission 
on Ventilation (1914), show the effects of heat, humidity, 
and stale air. It was found that when the temperature 
of the room was raised from 68° to 75°, the pulse and 
blood pressure were affected, and^the amount of physical 
work accomplished fell 15 per cent. None of these bad 
effects was felt if the room was kept cool, although the 



20 HOUSEHOI^D CHEMISTRY 

air was allowed to become stagnant for 8 hours, so that 
the carbon dioxide content increased to about 20 times 
the amount in pure air. A marked effect of this stale air 
on the subjects was, however, loss of appetite, although 
the odors accumulating in the room were not noticed by 
them. This sub-conscious result was proved by serving 
standard meals and calculating the amount eaten after a 
period spent in fresh air and in stale air. 

Methods of Ventilation. — Of the two methods of ven- 
tilation — natural and mechanical — the former is the one 
which must be depended upon in ordinary houses. 
Natural ventilation relies upon the movement of air 
currents caused by differences in temperature and grav- 
ity, and the force of wind — an uncertain agent. It takes 
into account the fact that air becomes lighter when 
heated, and rises. Heated 50° F. above the outside air, 
the air of a room will be increased one-tenth in bulk, 
since it expands ^/goo of its volume for every degree 
Fahrenheit. Consequently, since good ventilation re- 
quires a constant supply of pure air and a corresponding 
removal of foul air, there should be an inlet and an outlet, 
the latter at the top of the room where the heated air 
can escape, the former nearer the bottom, where the 
colder air entering can have an opportunity of circulat- 
ing through the room and pressing the warmer air up- 
ward. The problem of ventilation in winter often be- 
comes a question of draughts. If the inlet is arranged 
so that the air may pass in a vertical direction over the 
heads of the occupants of the room, and at the same 



HOUSEHOLD CHEMISTRY 21 

time be somewhat warmed, this trouble is remedied. If 
the opened window is the only form of inlet possible, a 
direct draught can be prevented by placing a frame in 
the opening covered with some open mesh material such 
as cheesecloth. 

The inlets and outlets should be as far as possible 
from each other, so that air will not pass directly from 
one to the other without circulating. An outlet should 
properly have the motive power of heat or an exhaust, 
otherwise it may become an inlet for cold air. The wind 
acts uncertainly as an exhaust at times; a mechanical 
arrangement is more dependable. A fireplace is a de- 
sirable natural outlet, having the extra motive power of 
heat. 

Heating by hot air is favorable to a good scheme of 
ventilation, provided (i) that a steady supply of pure 
air from outside is brought in to be heated and circulated 
through the flues; (2) that an outlet for foul air be 
provided in the room. 

Stoves, steam and hot water heating systems offer little 
aid to ventilation. On the contrary, stoves withdraw 
the purer air near the floor for purposes of combustion. 
Careful attention to ventilation is necessary with these 
methods of heating. 

Too often people live in tightly shut rooms in winter 
because they cannot afford loss of heat by ventilating 
openings. The injury to health is apparent in even a few 
weeks, in lessened vitality, susceptibility to colds, and 
actual disease. In such cases occasional throwing open 



22 HOUSEJHOLD CHEMISTRY 

of windows with rapid exercise at the time answers the 
purpose with less loss of heat. If one can become accus- 
tomed to free circulation without draughts, the body tone 
is raised so that less heat is required and the chances of 
injury on exposure are lessened. 



CHAPTER III. 



WATER. 

Water, or hydrogen monoxide, the universal solvent, 
was believed to be an element until the experimental work 
of Cavendish showed it to be the product of the chemical 
union of hydrogen and oxygen. The proportions in 
\7hich these gases combine are two parts of H to one of 

by volume, and one to eight by weight. 

Physical Properties. — Latent Heat. — Water exists in 
three states without change of composition : as a gas 
(steam) at ioo° ;^ as a liquid (water) between o° and 
ioo°, and as a solid (ice) below o°. In passing from 
the solid to the liquid state, additional energy is required 
for increased molecular spacing and motion. This is 
obtained in the form of heat from surrounding objects, 
and becomes the latent heat of fusion. The amount of 
heat transformed in this way in melting i gram of 
ice is sufficient to raise the temperature of i gram of 
water from o° to 80°, or 80 calories. Conversely, when 
water freezes, 80 calories per gram are released and ap- 
pear as sensible heat.^ 

Steam being a gas, requires more energy for molec- 

^ Unless otherwise stated, the centigrade scale is used in giving 
thermometer readings. 

' I Calorie = 1,000 calories. The British thermal unit (B. T. U.) 
is the quantity of heat required to raise i pound of water 1° F. 

1 Calorie is about equal to 4 B. T. U. as follows : i kilogram = 
2.2 pounds, 1° C. = 1.8° F. ; therefore i Calorie = 2.2 X i-8 = 
3.96 B. T. U. ; I calorie — 0.00396 B. T. U. 



24 HOUSEHOLD CHEMISTRY 

ular spacing and motion. To change i gram of water 
at ICMD° to steam at 100° necessitates approximately 
537 (536.6) calories. One gram of steam, therefore, 
contains 537 calories plus the 100 calories of the boiling 
water. When steam at 100° condenses to water at 100° 
537 calories are given up as heat. 

Specific Heat. — The capacity of water for heat is so 
great that it is taken as the standard. The specific heat 
of water is expressed as i ; that of most other substances 
in fractions. For instance, the specific heat of alumin- 
ium is 0.21, which means that the amount of heat which 
will raise i gram of aluminium 1° will raise i gram of 
water 0.21°. 

Conductivity, — Pure water is a poor conductor of 
heat and electricity, but dissolved matter increases its 
conductive capacity. 

Boiling and Freezing Points. — The boiling and freez- 
ing points of pure water under standard atmospheric 
conditions are used as convenient points for standard- 
izing thermometer scales ; in the Centigrade o°-ioo° ; in 
the Fahrenheit 32°-2i2°; in the Reaumur o°-8o°. An 
increase in atmospheric pressure raises the boiling point, 
a decrease lowers it. Boiling and freezing points are 
also affected by substances in solution. Solutions having 
increased density boil at a higher temperature and freeze 
at a lower than pure water. If electrolytes are in solu- 
tion the increase and decrease are greater than in the 
case of non-electrolytes. For example, the boiling and 
freezing points of a solution of sodium chloride are 



HOUSEHOLD CHEMISTRY 2^ 

higher and lower respectively than those of an equivalent 
solution of sugar. 

Density. — The weight of i cc. of water at its point of 
greatest density, 4°, is i gram. This is taken as the 
standard of density, and is used as the unit in specific 
gravity measurements of liquids and solids. The so- 
called Baume hydrometer, an instrument used for deter- 
mining the specific gravity of liquids, is made in two 
types — for light and heavy liquids. The zero mark in- 
dicates the floatation in distilled water at 60° F. for 
heavy liquids, and in a 10 per cent, salt solution for light 
liquids. To convert into actual specific gravity see page 

235. 

Compressibility and Expansion. — Water in the liquid 
state is practically incompressible. It is calculated that 
the small compressibility of water causes a lowering of 
the surface of the ocean to the extent of 600 feet where 
the depth is 6 miles, or an average depression for the 
large ocean bodies of 116 feet. On passing toward the 
solid state, water contracts until it reaches 4°, its point 
of greatest density. Below this point its volume in- 
creases, and at freezing point, 0°, there is a sudden 
further expansion of 10 per cent. Consequently water 
at 4° is heavier than at 0°, a provision of nature which 
makes it impossible for large bodies of water to freeze 
solid. When water is converted into steam it expands 
more than most other known liquids. The expression 
"a cubic inch of water makes a cubic foot of steam" is 
approximately true. 

Chemical Properties. — As a chemical agent, water is 



26 HOUSEHOLD CHEMISTRY 

extremely potent. It acts usually as a solvent, but in 
many cases produces profound chemical changes. 
Briefly, the action of water may be classed as follows : 

Water of Solution 

Water of Hydration 

Water of Hydrolysis. 
Water of Solution. — When any soHd dissolves in 
water, loss or gain of heat is apparent, but on evapo- 
rating the liquid the solid reappears in the original form. 
With acids, bases and salts there is electrolytic dissocia- 
tion in addition to solution. 

Water of Hydration. — On partial evaporation of the 
liquid, the soluble substance reappears in changed form, 
containing a definite amount of the water in the solid 
state. This is known as water of hydration or crystal- 
lization. Familiar examples are washing soda, Na2C0.i, 
loHaO; alum, K2AI2 (804)4, 24H2O; borax, Na2B407, 
10H2O; Glauber's salt, Na2S04, sH^O, and copper sul- 
phate, CUSO4, 5H2O. 

Water of Hydrolysis. — Complete hydrolysis is a change 
in which water enters a substance as H and the hydroxyl 
OH, splitting it into new compounds generally simpler 
than the original substance. The changes which food 
undergoes in the processes of digestion are examples of 
hydrolysis, such as the breaking down of sucrose into 
fructose and glucose : 

C,H,0, + H,0 — 2C,H,A. 

The solution of the non-metallic oxides SO3, N^Og and 
P2O5 is another example: 



HOUSEHOI.D che;mistry 2y 

SO3 + H,0 «-- SO^CHO), or H,SO,. 
NA + H^O — 2NO2HO or 2HNO3. 
. PA + 3H,0 — 2PO(HO)3 or 2H3PO, 
or the solution of caustic alkalies and slaking lime : 
Na,0 + H,0 «-- 2NaOH. 
CaO + H,0 — Ca(OH),. 
Applications. — Explain the principle of the ice box, 
the fireless cooker, the double boiler, the vacuum pan, the 
digester kettle, the unglazed water jar, the freezing mix- 
ture of ice and salt. 

Why are cranberry bogs flooded in winter, or tubs of 
water put in vegetable cellars or under orange trees on 
frosty nights? 

Explain the effectiveness of steam heating, hot water 
heating, a hot water bag. 

Why is salt put on an icy sidewalk in winter? 
Why is a scald from a steam burn worse than one 
from boiling water? 

Why does water boil more quickly when there is con- 
siderable water vapor in the atmosphere? 

How does adding salt to the water in boiling vege- 
tables and keeping the cover on the dish affect the boiling 
point ? 

Why is a mixture of ice and salt more effective than 
ice and sugar in freezing ice cream? 

Explain the cooling effect of perspiration. 
EXPEEIMENTS ON WATEB. 

I. Heat Condnctivity — Fill an 8-inch test tube two-thirds full 
of water, grasp the lower end of the tube with the fingers and 
hold in the flame at a slight inclination from the perpendicular. 
3 



^8 HOUSEHOLD CHEMISTRY 

Note that the upper part will boil before the lower becomes 
uncomfortably hot to hold. Reverse the order of heating and 
note the same result. Explain, 

2. Boiling Point Under Atmospheric Pressure. — Pour about 
250 cc. of distilled water into a half-liter round bottom flask 
supported on a ring stand. Introduce a thermometer so that the 
bulb only is immersed in the liquid and apply heat. Note the 
point to which the mercury rises when the liquid is quietly boil- 
ing, raise the thermometer bulb just out of the liquid and take 
the reading. Is there any difference? Does the thermometer 
indicate any higher degree of heat when the liquid boils 
violently ? 

3. Boiling Point Under Reduced Pressure Select a cork 

which fits the flask closely, pierce a hole through it and insert a 
thermometer. Fill the flask one-third full with water and boil 
the liquid. When in active ebullition, close the flask with the 
cork and thermometer and instantly withdraw the heat. When 
the liquid ceases to boil, read the thermometer, and grasping the 
neck of the flask with several folds of a towel, hold it under 
running cold water. What happens? Read the thermometer and 
explain. 

4. Convection. — Water may be made to show the path of travel 
of convection currents as follows: 

Fill a 500 cc. beaker two-thirds full of distilled water, place 
over wire gauze on a ring stand and apply heat by placing the 
Bunsen burner on one side of the bottom. When the water is 
warm drop into it a few crystals of f uchsin or other soluble color- 
ing matter and watch the path of the crystals through the water. 

5. Influence of Soluble Matter. — Note the boiling point of a 
solution of 10 grams of salt in 100 cc. of distilled water. Ob- 
serving the same conditions throughout, repeat the experiment, 
using sugar. How do the boiling points compare? Explain. 
Cool each solution to 15° and take its specific gravity. 



HOUSEHOLD CHEMISTRY 29 

6. Take the specific gravity of a mixture of equal volumes of 
water and 95 per cent, alcohol, and note its boiling point. 
Explain. 

7. Weigh out 30 grams of table salt, measure 100 cc. of dis- 
tilled water, and use only as much of the water as is required 
to make a saturated salt solution (pickle). What is the required 
proportion of salt to water? Take the specific gravity of the 
solution and its boiling point, and compare with Experiment 5. 
Will a fresh egg float or sink in this liquid? Evaporate a few 
drops of the solution on a microscope slide and observe the salt 
crystals under a low power lens. 

8. Hydration and Hydrolysis — Take a tablespoonful of com- 
mon plaster, mix this with half the volume of water in a porce- 
lain dish, stirring with a thermometer. Record the result and 
explain. 

9. Slowly pour about 10 cc. of strong sulphuric acid into 50 cc. 
of cold water, stir well with a thermometer, and from time to 
time record the temperature. Explain. 

10. Using a burette, carefully mix exactly 52 volumes of alco- 
hol (95 per cent.) and 48 volumes of water in a 100 cc. stop- 
pered cylinder. How many volumes result? Explain. 

11. Add half a teaspoonful of dry pulverized Hme (CaO) to 
an equal volume of cold water, stir the mixture with a ther- 
mometer, adding more water if necessary, and record the ther- 
mometer reading. Explain and write reaction. 



Potable or Drinking Water. 

Classification of Natural Waters. — Natural waters are 
never pure, as they dissolve or hold in suspension gases, 
liquids, and solids with which they come in contact. The 
following is a convenient classification : 



30 



HOUSEHOLD CHEMISTRY 



Natural 



Waters 



f Rain 
' Atmospheric < Snow 
I Fog 



Terrestrial 



-Contains very little dis- 
solved solids but dust 
and gases of the atmos- 
phere. 

' Surface — Cloudy, usually a 
large amount of suspended 
matter, minimum of dis- 
Sweet ■{ solved. 

Underground — Clear, m i n i - 
mum of suspended matter, 
maximum of dissolved. 



{ Brines— over 5% soluble salts. 
Salt I Sea water— 3.6% solids. 

Mineral — excess of, or unusual 
mineral matter and gases. 

Potable or drinking water should be clear, free from 
odor and color, and should not contain in excess of 20 
grains of solids per U. S. gallon, of which not more 
than one-half is organic matter. 

The soluble mineral matter in water consists of a 
mixture of the following salts : 

Carbonates I f Sodium 

Bicarbonates ! r J Potassium 

Sulphates | j Calcium 

Chlorides J I Magnesium 

together with oxide of iron and silica in minute amounts. 
An excess of chlorides may be due to sewage or animal 
contamination, excess of lime causes hardness, and excess 
of iron usually is apparent from the color and is probably 
due to the solvent effect of organic matter in the water. 
On boiling, water loses its dissolved gases, hence dis- 
tilled or sterilized water is flat or stale. 

Qualitative Examination of Water. — The importance of 
guarding a water supply from contamination is evident. 
Equally important are frequent expert analyses of the 



HOUSEHOI.D CHEMISTRY 3 1 

supply in order to be sure that the safeguards used are 
effective. No attempt will be made in this book to give 
methods for the quantitative estimation of the impurities 
found in water. However, certain qualitative tests 
are suggested which will aid in detecting such impurities 
when present in abnormal amounts ; it is only when found 
in such amounts that the water is open to suspicion. The 
impurities are for the most part harmless in them- 
selves, but if found demand quantitative analysis and 
possibly bacteriological examination. A thorough in- 
vestigation of the surroundings and of the sources of 
contamination of the supply, and great care in taking the 
sample, are essential in making an examination of any 
water. 

The tests usually made are with regard to color and 
appearance, odor and taste, and for the presence of total 
solids, free and albuminoid ammonia, nitrogen as nitrites 
and nitrates, chlorine, temporary and permanent hard- 
ness, and sometimes phosphates, sulphates, etc. 

The color and turbidity, odor and taste of a drinking 
water are not in themselves indications of its purity, but 
taken with other data, help in forming an opinion of the 
sample. A clear, colorless, tasteless water may be pol- 
luted ; on the other hand a safe water may have acquired 
color from dissolved iron, a "peaty" taste from swamp 
vegetation, or a fishy odor from the decay of algae. 

Odor. — Rinse a stoppered flask with the water to be tested, 
fill it two-thirds full of the sample, cork, shake violently, remove 
the stopper and note the character and intensity of the odor. 
Replace the cork, warm the water over a water bath to 40", 
remove, again shake thoroughly and observe the odor as before. 



32 HOUSEHOLD CHEMISTRY 

The odor will be strengthened by heating. A putrid or offensive 
smell probably indicates sewage contamination. 

Color and Turbidity. — Fill one of two Nessler's tubes with the 
water under test, the other with an equal volume of distilled 
water. Compare the color and clearness of the two by observing 
against white paper. 

Total Solids. — ^This is a method of determining the 
total residue left by the water on evaporation, and the 
proportion of mineral and organic matter present. The 
follov^ing experiment gives an approximate estimation^ 
of total solids : 

1. Weigh a clean porcelain dish, measure into it loo cc.'^ of 
the water to be tested, and evaporate to dryness over a water 
bath. Cool and weigh. The increase in weight gives total solids. 
Apply gentle heat and notice any charring (due to organic 
matter). A sour odor at this point indicates sewage contamina- 
tion; a peaty odor, the presence of swamp water. Continue heat- 
ing until the residue is white or nearly so ; cool and weigh. The 
loss in weight represents organic matter and COa due to bicar- 
bonates; the residue is mineral matter. Some inaccuracy must 
be expected, due to the action of heat in volatilizing alkali 
chlorides. 

2. Concentrate loo cc. of the water to about lo cc, cool and 
test for mineral matter as follows ; 

(a) Phosphates. A few drops of the liquid, acidified with 
HNO3, is added to a larger quantity of ammonium molybdate and 
heated in boiling water. A yellow crystalline precipitate, ammo- 
nium phosphomolybdate, indicates phosphates. Phosphates are 
seldom found in drinking water. If present they indicate prob- 
able sewage contamination. 

^ For exact methods, see Air, Wafer and Food, Richards and 
Woodman, and Examination of Water for Sanitary and Tech- 
nical Purposes, Leffmann and Beam. 

^ If 100 cc. are evaporated, the residue in milligrams represents 
so many parts per 100,000; if 58 cc. are taken, each milligram 
of residue is equivalent to a grain per U. S. gallon. 



HOUSEHOI.D CHEMISTRY 33 

(b) Chlorides. Add a drop of HNO3, then AgNOg. A white 
precipitate of silver chloride, AgCl, soluble in NH4OH, indicates 
chlorides. 

(c) Sulphates. Make faintly acid with HCl and add a few 
drops of BaCk A white crystalline precipitate, BaS04, insoluble 
in HCl indicates soluble sulphates. 

(d) Carbonates. To 40 or 50 cc. of clear lime water add a 
small amount of the original sample. Any cloudiness soluble in 
acetic acid indicates carbonates. Make the flame test on the con- 
centrated water. A yellow color indicates sodium; a violet, 
potassium. View the latter through blue glass. 

(e) Iron as ferric compounds. Slightly acidify with HCl and 
add NH4SCN. A blood red color, Fe2(SCN)6 indicates iron. 
Or, to determine the oxidation of the iron, to the acidified water 
add K4Fe(CN)6. A dark blue color indicates ferric salts. With 
K3Fe(CN)6 a blue color indicates ferrous compounds. 

(/) Calcium. Add NH4CI, NH4OH, and (NH4)2C204. A 
white crystalline precipitate of calcium oxalate, CaC204, soluble 
in HCl, forms on boiling. If calcium is present, filter, and save 
the filtrate for (g). 

(g) Magnesium. To the above well cooled filtrate add sodium 
phosphate and shake vigorously. After standing, magnesium 
shows as a white crystalline precipitate of ammonium magnesium 
phosphate, NH4MgP04. 

(h) Aluminium. Add NH4CI and an excess of NH4OH. 
Warm the solution. A white flocculent precipitate of aluminium 
hydroxide, Al(OH)s, appears on standing, if considerable alum 
is present. The logwood test (p. 175) is more delicate for small 
amounts. 

Free and Albuminoid Ammonia. — Two forms of am- 
monia are looked for in water — free and albuminoid. 
Neither of these is injurious in itself, but their sig- 
nificance lies in the fact that they indicate conditions 
favorable for pathogenic bacteria. The free or ureal 
ammonia, if present in any quantity, is considered to 



34 HOUSEHOLD CHEMISTRY 

show recent sewage pollution, as, although it is found in 
rain water, and may be formed by the decay of certain 
algae, it is directly associated with animal excretions, 
e. g., urea. Urea readily yields free ammonia as fol- 
lows: 

(NH,),CO + 2H,0 — (NHJ.CO,. 

(NHJ,C03 ^ 2NH3 + H,0 + CO,. 
Since ammonium carbonate decomposes as above on 
heating, it is evident that free ammonia can be obtained 
by simply boiling the water. 

Albuminoid ammonia will not volatilize by this treat- 
ment. When present, it indicates undecomposed organic 
nitrogen, generally as low forms of plant life. It is 
necessary to oxidize these substances to volatile com- 
pounds before this form of ammonia can be obtained by 
distillation. 

, Determination of Pree and Albuminoid Ammonia. — 
The method to be followed is distillation, successive dis- 
tillates to be obtained and tested with Nessler's solution, 
which gives a yellow or brown color in the presence of 
ammonia. 

Directions. — Thoroughly cleanse and rinse with distilled water 
a round bottom half-liter flask and a number of 6-inch test 
tubes. Connect the flask with either a condenser or a long piece 
of glass tubing arranged to deliver into the receiving test tubes, 
which in this case must be cooled by running water or ice. Make 
all connections tight. Fill the flask about two-thirds full of the 
water to be tested, add 5-10 cc. of NaaCOs solution and distil 
with moderate heat. Collect the distillates in equal amounts, 
about 15 cc, in successive test tubes, and add to each the same 
number of drops of Nessler's solution. Observe any deepening 
of color by looking down through the tube against a white back- 



HOUSEHOLD CHEMISTRY 35 

ground. The color may be compared with standard ammonia 
solutions. Continue the distillation until a sample shows no 
color with Nessler's. Save the distillates for comparison with the 
yield of albuminoid ammonia in the following: 

Cool the balance of the water in the flask and add alkaline 
potassium permanganate in the proportion of about 5 cc. to 
200 cc. of water. Distil with steady moderate heat, collect and 
test successive distillates as before. The alkaline permanganate 
solution oxidizes the nitrogen in the form of albuminoid ammo- 
nia to compounds yielding free ammonia. 

Nitrites and Nitrates. — The presence of nitrites in 
water is supposed to be due either to the incomplete 
nitrification of ammonia or to the reduction by micro- 
organisms of nitrates already formed. While traces of 
both may occur in all natural waters, a large quantity 
suggests previous pollution by nitrogenous organic mat- 
ter of animal origin. This material begins the nitrogen 
cycle; by decomposition and the work of micro-organ- 
isms ammonia compounds follow, and these in turn are 
oxidized by aerobic organisms to nitrites. Further 
oxidation by another group of organisms converts these 
into nitrates. If now nitrates come within reach of 
chlorophyll bearing plants, they complete the cycle by 
converting the oxidized nitrogen back to organic nitrogen 
again. The importance of nitrite and nitrate determina- 
tion in studying a water supply is evident. 

In one of three 6-inch test tubes put 20 cc. of nitrite-free water 
(use distilled), in another the same amount of the water under 
test, in the third nitrite water (to be furnished by the instructor). 
To each add i cc. of a freshly prepared mixture of equal parts 
of sulphanilic acid dissolved in acetic acid, and naphthylamine 
acetate dissolved in dilute acetic acid. Mix and allow to stand 



36 housi:hoi,d chemistry 

30 minutes. If the solution becomes pink the water contains 
nitrites. 

Chlorides. — Chlorine is found mostly as sodium 
chloride, although other chlorides may be present. The 
amount of sodium chloride in any given water supply is 
affected by the character of the soil, proximity to the 
ocean, etc., but it should be constant for the locality. 
Any marked increase over the normal figure indicates 
sewage contamination. 

Place in a small casserole or porcelain dish about 100 cc. of 
the water to be tested, and in another dish the same amount of 
distilled water. Add to each 2 or 3 drops of potassium chromate 
solution, then add drop by drop a dilute solution of silver nitrate 
(N/io), stirring after each drop until a faint tinge of red 
remains. Obtain the same tint in each, and note the number of 
drops of silver nitrate used in each case. Each drop of silver 
nitrate solution is equivalent to 0.000293 gram sodium chloride. 

Oxygen Consuming Power. — This is a method of esti- 
rnating the organic matter in water by its decolorizing 
power in the presence of potassium permanganate. The 
test is not especially significant even when performed 
quantitatively, as it is not delicate or definite. 

Fill two clean 6-inch test tubes, one with the water to be tested, 
the other with distilled water, and add to each the same amount 
of acidified potassium permanganate solution. Be careful not to 
obtain too deep a tint and see that the shades match. On stand- 
ing ID minutes, there should be an appreciable lightening in color, 
greatest in the tube of water under test. If the color entirely 
disappears, the amount of organic matter is probably dangerously 
great. Compare with the test under total solids. 

Ice used in drinking water should be examined as to 

purity. A sample may be melted and tested by the 

method described for water. 



HOUSEHOLD CHEMISTRY 37 

Water Purification. 

Household Methods.^ — Boiling. — Boiling is the simplest 
and most effective household method of making a drink- 
ing water safe, as typhoid and other pathogenic bacteria 
are killed. Boiled water has a flat taste due to the loss 
of dissolved gases, but this can be remedied by aeration. 

Effect of Charcoal. — Charcoal is useful as a decolor- 

izer and deodorizer. 

To 50 cc. of water add enough vinegar to give it a distinct but 
not deep yellow color, then divide into two equal parts. Filter 
one through dry freshly ignited boneblack several times and com- 
pare the color of the resulting liquid with the original solution. 

Effect of Alum. — ^Alum readily ionizes in water, 

forming a flocculent precipitate of aluminium hydroxide, 

which collects any suspended matter and removes it by 

sedimentation. It is thus useful in clearing turbid water 

for laundry purposes, swimming pools, etc., and is used 

on a large scale in some filtration beds. 

Take any sample of cloudy or slightly colored water, even 
soapy water will answer. Add a very small quantity of finely 
powdered alum, shake well, filter, and compare with the original 
sample. Write the reaction for the formation of aluminium 
hydroxide. 

Water should be neutral or slightly alkaline to work 
well with alum. 

Filtration. — Prove by the following experiment the 
effect ordinary filtration has upon substances in solution 
or suspension in drinking water : 

Filter a dilute salt solution; taste the liquid. Is any change 

^For public methods of water purification, see Food Industries, 
Vulte and Vanderbilt, and Our Water Supply, Mason. 



3^ HOUSEHOLD CHEMISTRY 

produced? Add to the filtrate a few drops of AgNOa, shake 
well and filter again. Note any difference. 

Household filters of the Berkefeld, Pasteur-Chamber- 
land and Aqua Pura types are effective, as they remove 
micro-organisms as well as suspended matter. 

Distillation. — This is an effective method of purifying 

water, but not so simple for household practice as boiling. 

From the following experiment the student is expected 

to determine the effect of distillation with reference to 

volatile and non-volatile substances: 

Using the same apparatus as for the determination of ammonia, 
distil with moderate heat a solution of about 2 grams of copper 
sulphate in 250 cc. of water. Is this solution acid? Carefully 
examine the distillate for copper sulphate. Remove the burner, 
cool the apparatus, and add 5 cc, of ammonia, shaking well ; a 
deep blue color should be obtained. Distil this liquid and test 
the distillate as before. Explain. 

Hard and Soft Water. 

With reference to its detergent action, two kinds of 
water are recognized — hard and soft. Hard waters con- 
tain calcium and magnesium salts which are undesirable 
in many industries. They produce the troublesome 
boiler scale, they are a serious objection in sugar refin- 
ing, and in many textile operations, especially in dyeing. 
In the household hard water makes a poor detergent, 
because soluble calcium and magnesium salts form in- 
soluble compounds with soap, which not only have no 
cleansing value, but produce a troublesome curd. A 
certain amount of soap must be lost in this way before 
a lather will form and cleansing begin. The degree of 
hardness a water possesses may be measured by its soap- 



HOUSEHOLD CHEMISTRY 39 

destroying power. The total hardness of most water is 
of two kinds — temporary and permanent. 

Temporary Hardness. — This form is caused by carbon- 
ates of calcium and magnesium held in solution as bi- 
carbonates by carbon dioxide present in the water. Boil- 
ing expels the CO^, causing a precipitation of calcium 
and magnesium carbonates, and the temporary hardness 
is removed. Calcium hydroxide is often used on a large 
scale for the same purpose. Its effect can be shown as 
follows : 

Ca(0H)2 + CaCHCOg), — 2CaC03 + 2H,0. 
Pass a current of CO2 gas into a small amount of lime water 
until the precipitate clears. What was the precipitate? What 
does the water now contain? Write the reactions. What hap- 
pens if more lime water is added? Write the reaction, and show 
that for every nine parts of hardness four parts of Ca(0H)2 
are required. 

Permanent Hardness. — Permanent hardness is due to 
the presence of calcium sulphate and other soluble salts 
of calcium and magnesium, not carbonates, held in solu- 
tion by the solvent action of the water itself. Such a 
water cannot be affected by boiling, but may be soft- 
ened as follows: 

1. Prepare a hard water by dissolving o.i gram of calcium 
sulphate in 500 cc. of distilled water. Add sodium carbonate 
solution to a portion, and note the result. Write the reaction. 
Filter and save the filtrate. 

2. Roughly determine the amount of soap solution necessary 
to make a lather lasting 5 minutes in (a) 50 cc. of the above 
filtrate, and (b) an equal amount of the untreated hard water. 
What is the effect of the NaaCOa? 

Quantitative Estimation. — To estimate the total hard- 



40 HOUSEHOIvD CHEMISTRY 

ness of a given water the procedure may be as follows : 

Make a standard soap solution by dissolving lo grams of good 
castile soap in sufficient 90 per cent, ethyl alcohol to make up to 
I liter. For use mix 100 cc. of this soap solution with 100 cc. 
of distilled water and 30 cc. of 95 per cent, alcohol. 

Put 58 cc. of the water under test in a clean stoppered 8-ounce 
bottle, add the soap solution ^ cc. at a time, shaking thoroughly 
after each addition. Continue until a lather is formed which 
will cover the surface of the liquid when the bottle is placed 
on its side, and will last 5 minutes. Note the amount of soap 
solution used. 

Estimate the total hardness of the water in grains per 
gallon by using the following data : 

One U. S. gallon contains 58,318 grains, 58 cc. contains 
58,000 milligrams. Therefore, 58 cc. represents a minia- 
ture U. S. gallon, and i milligram per 58 cc. stands 
for I grain per gallon, approximately. One cc. of the 
standard soap solution is the equivalent of i milligram 
of Ca, calculated as CaCOs. 

For example, if 10 cc. of soap solution are used, a 
gallon of the sample contains 10 grains of Ca, spoken of 
as 10° of hardness. This will be the total hardness of 
the water. 

To estimate the temporary hardness, boil 58 cc. of the sample 
for I or 2 minutes, cool to the temperature of the unboiled water, 
and make up with distilled water the loss by evaporation. Add 
the soap solution as before and note the amount required, now 
that the temporary hardness has been removed. In this case 
the permanent hardness has been overcome by the soap solution, 
and the difference in the amounts of the soap solution used in 
the two cases is the measure of the temporary hardness of the 
water. 

Use of Washing Soda. — ^Washing soda is cheaper and 



HOUSEHOI^D CHEJMISTRY 4I 

more efficient than soap in softening hard water. The 
following equations show the ratio of efficiency between 
the two: 

(1) CaSO, + Na^COg »-> CaCOj + Na^SO^. 

136 106 > — , — ' 

(2) CaSO, + aCi^Hj^COONa »-> 

136 612 

(C,,H3,C00),Ca + Na,SO,. 

« , 1 

Therefore 612 pounds of pure soap are required to do 
the work which 106 pounds of washing soda will do, 
making a ratio of 6:1. But since much yellow laundry 
soap is only about one-third actual soap, the balance 
being resin, water, and other substances, the ratio be- 
comes 18:1, and in actual practice i pound of washing 
soda is considered equivalent to 18 or 20 pounds of soap 
A white laundry soap of good quality averages about 75 
to 85 per cent, actual soap. 

Problem. — ^A water contains 15 grains (approximately 
I gram) of Ca per gallon. How much of NagCOg, white 
soap, and yellow laundry soap will be required to over- 
come the total hardness^ of 500 gallons? Assume that 
the 15 grains of calcium are in the form of calcium sul- 
phate. 

Natural soft waters are usually recommended for the 
laundry, solely because they are lacking in soluble lime 
and magnesia compounds which would waste soap. But 
organic matter present in this class of water, through 
stagnation or from soil rich in humus, dissolves notable 

^ For exact methods of hardness determination, see Hehner's 
alkalimetric method in Examination of Water by Leffmann and 
Beam. 



42 HOUSEHOI^D CHEMISTRY 

quantities of metallic oxides from containers and con- 
duits, so that water of this class may become hard from 
the presence of soluble organic salts of such elements as 
iron, lead, copper, tin, zinc, etc. In the usual hot water 
supply of the household this is noticeably the case. So 
that a moderately hard water — temporary hardness best 
for the cold supply — which will deposit insoluble lime 
compounds on the exposed metallic surfaces, is a safe- 
guard. Probably the ferrous compounds of iron are the 
worst to deal with, as they usually are not noticeable 
from lack of strong color, but readily show in the oxi- 
dized form as iron rust spots after drying and ironing 
white garments. If iron is present it should be com- 
pletely removed, either by long boiling and settling or 
filtering, or by adding washing soda, borax, or ammonia, 
then boiling and settling. Organic matter may be dis- 
closed by the permanganate test. If present in consider- 
able quantity it would be well to oxidize both the fer- 
rous compounds and the organic matter by means of 
additional permanganate and heat, finally settling or fil- 
tering, to remove any residue. 



CHAPTER IV. 



METALS. 

The aim of this chapter is the study of the physical 
and chemical properties of metals, rather than of their 
compounds, especially with regard to their use in the 
household. Therefore only those in common use will 
be considered. Such metals are iron in its various forms, 
nickel, zinc, copper, aluminium, silver, lead, tin and cer- 
tain alloys. 

Iron, (Ferrum) Fe, occurs in nature largely in the 
form of oxides: haematite, FeaOg (red), and magnetite, 
FegO^ (black), the latter possessing magnetic qualities 
and commonly called lodestone. 

The metal is obtained by fusing the ore in shaft fur- 
naces with excess of carbon and enough limestone to 
furnish a fusible ash or slag with the silicious matter 
present in the ore. The following equations explain the 
reduction and slagging: 

2Fe30, + SCO ^ 3Fe, + SCO,. 
SiO, + CaO «— CaSiOg. 
The product, "pig iron," or crude cast iron, contains 
from 3-4 per cent, of carbon as graphite and combined 
carbon or carbide of iron, FcgC, rendering the mass 
fusible. By careful smelting in small shaft furnaces 
called "cupolas," the pig iron is obtained in the form of 
gray, white and mottled iron, depending on the rapidity 
of cooling the moulds. Pig iron frequently contains 
small amounts of impurities, sulphur and phosphorus, 
4 



44 HOUSEHOLD CHEMISTRY 

rendering the product short or brittle, while hot or cold ; 
during the refining process these are almost entirely 
removed in the slag. 

Cast iron is brittle and hard, it melts without soften- 
ing at 1,200° and yields a thin liquid which may be cast 
in sand moulds. The quality of the product depends 
largely on the purity of the iron (freedom from S. and 
P.), its temperature of cooling, and the smoothness of 
the mould. 

Cast iron heats more slowly but retains its heat better 
than other forms of the metal, hence its use for oven 
plates, sad-irons, stove lids, etc. If heated repeatedly to 
redness in presence of air and quickly cooled its carbide 
content increases at the expense of the graphite, and it 
becomes whiter and more brittle. This causes the fre- 
quent cracking of old stove lids. Slow cooling allows 
less carbide to form ; as a result the lid is less brittle, less 
liable to crack, and has a darker appearance. On the 
other hand, the hardness of carbide is desirable in sad- 
irons, accordingly they are frequently heated to a high 
temperature and plunged into cold water. Cast iron can 
be made harder than steel, and is sometimes used for the 
wheel in glass cutters. It does not oxidize as readily as 
steel or wrought iron. 

Malleable iron is intermediate between cast and 
wrought iron. It is made by slowly cooling cast iron to 
increase its graphite content and elasticity. It is there- 
fore softer and less brittle than ordinary cast iron, and 
is much used in house hardware. 



HOUSEHOI.D CHEMISTRY 45 

Wrought iron and steel are prepared from pig iron 
by burning out part of the carbon in hot air furnaces of 
special construction. The reverberatory furnace for 
producing wrought iron is really a large oven heated by 
gas and provided with a powerful blast of hot air. 
Liquid pig iron is run on to the hot furnace bed where 
the excess of oxygen removes the carbon as follows : 

Cj + O2 »-^ 2CO. As the CO escapes from the liquid 
mass it produces a bubbling like any boiling liquid. 
Gradually as the carbon is burned out, the iron becomes 
pasty or semi-solid and is collected in balls with large 
pokers operated by hand (puddling). When the balls 
are of sufficient size they are removed with tongs, 
squeezed to remove slag and rolled into short bars 
(blooms or billets). The blooms are then reheated until 
soft and rolled in bars and rods ; when cold the bars may 
be drawn down through steel dies into wire of almost 
any degree of fineness. They are cold forged into nails 
and tacks. Piano wire, the purest form of iron, con- 
tains 99.7 per cent. Fe, the balance is mainly carbon. 
Cold wrought iron is quite soft, bends easily and has 
great tensile strength. It does not melt readily (i,6oo°) 
but softens on heating and may be forged and welded. 

Steel is a form of iron between cast and wrought, 
containing 1.5 per cent, carbon. When heated and slowly 
cooled it is soft (mild), but if suddenly cooled is harder 
than glass. Hardened steel cautiously reheated, may be 
softened to any desired extent (tempering). At a high 
temperature steel melts and may be cast like iron. 

Two kinds of steel are manufactured, i e., Bessemer, 



46 HOUSEHOI^D CHEMISTRY 

the cheaper variety used for rails, plate for making so- 
called sheet tin and galvanized iron, wire nails, etc., 
and open hearth steel, a more expensive variety used 
for cutlery and tools. 

Bessemer Process. — The cast iron is first melted in a 
cupola, and then run into a special furnace (the con- 
verter), where a powerful blast of hot air bubbles 
through the molten liquid and quickly (15 minutes) 
burns out the carbon and other impurities and even pro- 
duces some oxide. Just at this point, a small portion of 
molten cast iron containing manganese and the proper 
amount of carbon is added and the mixture immediately 
poured into the moulds and cooled. The function of the 
manganese is to assist in holding the carbon in solution. 

Open Hearth Method. — The cast iron is melted in a 
gas furnace with dish-shaped bed together with scrap 
wrought iron and iron ore. After 8 or 10 hours' heating, 
the operation is complete and the liquid steel is drawn 
off and cast in ingots. 

Steel rusts much more readily than cast iron and 
usually needs, especially if polished, a protecting coat 
of oil. Rust may be removed from iron or steel by soak- 
ing in kerosene and rubbing with fine emery or carbor- 
undum and oil, but stoves and sad-irons should not be 
coated with kerosene and allowed to stand, as unsat- 
urated compounds in the hydrocarbon take up oxygen 
and cause the iron to rust. 

Galvanized Iron. — See zinc. 

Properties of Iron. — Iron has a specific gravity of 7.8, 



HOUSEHOLD CHEMISTRY 47 

and when pure fuses at about i,8oo°. It is strongly at- 
tracted by magnets. In moist air it oxidizes readily, 
forming red oxide or common iron rust, FegOg. This 
oxide is soft and friable and does not protect the metal 
from further action. It is slightly soluble in water, 
giving it a characteristic taste, experienced in drinking 
water conducted by iron pipes. The other type of oxide, 
Fe304, is formed by the oxidation of hot iron, or by the 
action of superheated steam and carbon monoxide 
(Barff Process). FegO^ forms a dark gray adherent but 
brittle coat and protects the metal from further action. 
It is called the magnetic oxide or blacksmith's scale. 
Russia iron is sheet iron which has been given this lus- 
trous protective oxide coat. It is used for stovepipes, etc. 
The red oxide forms the basis of pigments such as Ven- 
etian and Tuscan red. 

Iron reacts readily with warm dilute acids, but resists 
the action of alkalies. 

EXPERIMENT. 

Boil small pieces of bright and rusty iron in separate test 
tubes in the following liquids: Dilute hydrochloric acid (i : i) ; 
20 per cent, acetic acid, and lo per cent, caustic soda solution. 
Note comparative strength of action. Filter off the liquid in 
each case, and test with ammonium thiocyanate in the presence 
of hydrochloric acid. A blood red color shows iron in solution. 
Record the results. Write reaction between FesCls and NHiSGN. 

Nickel, a hard white metal, occurs in the pure state 
only in meteorites, but is found combined in several 
minerals. It is obtained by smelting in the blast fur- 
nace. As it takes a high polish and is only slightly sus- 



48 HOUSEHOLD CHEMISTRY 

ceptible to oxidation in moist air, it is largely used as a 
protective and decorative coating for iron and copper. 
The method of plating nickel on iron is similar to silver 
plating. The bath contains ammoniacal nickel sulphate, 
(NH4)2S04,NiS04,6H20, in v^hich the article to be 
plated is suspended, after having been cleaned by acid. 
This forms the cathode, and a nickel plate the anode. 

Nickel plated articles should always be cleaned with 
a mixture of diluted ammonia and whiting, or rouge^ 
and polished with soft cotton waste. 

Nickel has a specific gravity of 8.8, and a melting point 
of 1,500^-1,600°. As an ingredient of alloys, nickel is 
found in German silver (nickel i part, zinc i part, cop- 
per 2 parts), and in coin nickel (copper 3 parts, nickel 

I). 

It is not active with dilute acids, and like iron resists 
'the action of alkalies. 

EXPERIMENT. 

Heat small pieces of pure nickel with dilute acids and alkalies 
as under iron and record the results. Soluble salts of nickel 
have a green color and yield a black precipitate, NiS, with 
ammonium sulphide. Neutralize acid solutions with NH4OH 
before adding (NH4)2S. Write reaction between NiCU and 
(NH4)2S. 

Pure nickel utensils are valuable in the household, but 
the initial cost is comparatively high. In the laboratory 
they form a desirable substitute for iron. 

Zinc occurs chiefly as calamine or zinc blende, ZnCOg. 
After calcination to drive off CO^, the oxide is mixed 
with carbon and distilled in earthen retorts at 1,300- 



HOUSEHOLD CHEMISTRY 49 

1,400°; crude metallic zinc "spelter" condenses in the 
receivers and CO burns at a small opening. 

ZnCOg «-- ZnO -f- CO^. 
2ZnO + C,^^ 2Zn + 2CO. 

Zinc is bluish white, highly crystalline and brittle when 
cold. By heating to 120-150° and rolling under hot 
rolls it remains pliable and soft on cooling (sheet zinc). 
At 200-300° it becomes brittle again, melts at 433° and 
boils at 920°. Its specific gravity is 7. 

Zinc burns in the air with a bluish white flame, yield- 
ing a white oxide which is the base of the pigment 
Chinese white. Zinc oxide is a common ingredient of 
face creams and other toilet preparations. 

In moist air, it oxidizes and absorbs CO2, forming a 
thin adherent coat of basic carbonate which protects the 
metal from further change. Dilute acids readily dis- 
solve this coating and thus restore the original brilliancy. 
Acids and alkalies freely attack zinc, liberating hydrogen 
and producing soluble compounds which are poisonous, 
hence zinc vessels should never be used for the prepara- 
tion or storage of food. Do not attempt to cleanse zinc 
or galvanized iron with anything but neutral soap and 
hot water. 

Sheet zinc is frequently used for roofs, gutters, cor- 
nices and leaders of buildings; but does not last well 
near the seashore, on account of the salt in the atmos- 
phere. 

The molten metal mixes in all proportions with cop- 
per, tin, and antimony. (See German silver, brass, etc.) 



50 HOUSEHOI^D CHEMISTRY 

Zinc, both cast and rolled, is largely used in primary 
batteries. It lasts much better if cleaned with dilute 
sulphuric acid and coated with mercury (amalgamated). 

EXPERIMENT. 

In a dilute salt solution immerse bright strips of sheet copper 
and zinc in metallic contact. Prove by examination of the liquid 
which element suffers by the action. If zinc is in the solution, 
potassium ferrocyanide will give a white flocculent precipitate 
of zinc ferrocyanide in acid solution. Test for copper by adding 
an excess of ammonium hj^droxide; a blue color shows its 
presence. 

Galvanized iron is sheet iron or steel which after being 
cleaned with acid is dipped in molten zinc. It is prac- 
tically a zinc article, resists rust, and should not be used 
as a receptacle for food. 

Copper. — Copper (cuprum^), Cu, is found native, also 
2ts sulphide and carbonate. Native copper ore is crushed, 
washed to remove rock and melted with flux. The metal 
usually contains a small amount of silver which is re- 
moved by electrolysis. Carbonates and oxides are fused 
with coal to reduce the metal. Sulphide ores containing 
iron require complex treatment; in Montana the pro- 
cedure is as follows : Partial oxidation by roasting, and 
subsequent fusion in Bessemer converter (with silicious 
lining) during which sand and air are blown through the 
molten mass. The iron is oxidized and combines with 
silica forming a slag, which floats on the copper. Sul- 
phur, arsenic and lead are oxidized and volatilized. 

* The term "cuprum" was derived from the island of Cyprus in 
the Mediterranean, where copper was first mined and extracted. 



HOUSEHOLD CHEMISTRY 5 1 

Copper is refined by electrolysis in the following 
manner: Thin copper sheets coated with graphite are 
suspended in tanks of copper sulphate solution and 
connected with the negative pole of the dynamo ; opposite 
are heavy plates of crude copper connected with the 
positive pole. Pure copper is deposited on the cathode, 
while the SO^ ionizes the anode. The impurities not 
ionized fall to the bottom of the tank. 

Properties. — Copper is a red metal melting at 1,057°. 
It is a good conductor of heat and electricity, is very 
malleable and ductile, and has a specific gravity of 8.9. 
Several oxides of copper are known ; two important ones 
are the black or cupric oxide, CuO, and the red or cuprous 
oxide, Cu^O. The latter forms slowly in dry air; in 
moist air green basic carbonate (not verdigris) is formed. 
Copper utensils are often lined with tin to prevent the 
formation of this coating. When free from oxide cop- 
per resists the action of alkalies, organic acids and most 
mineral acids, and is much in demand for the manu- 
facture of apparatus used in food preparation, e. g., 
vacuum pan for sugar, milk, etc., apparatus for canning 
and preserving, candy making and beer brewing. Large 
hotels and restaurants use copper cooking utensils. 

The most important alloys of copper are: 

Brass, containing 18-40% Zn 

Bronze, containing ^ 11% Zn, 3-8% Sn, some Pb 

Gun metal, containing 10% Sn 

Bell metal, containing 25% Sn 

German silver, containing 19-44% Zn, 6-22% Ni 

Brass is essentially like copper in its properties. 
Metallic copper and its alloys are readily cleaned with 



52 HOUSEHOI^D CHEMISTRY 

dilute oxalic acid or ammonia. In the laboratory tar- 
nished copper may be cleaned as follows : 

EXPERIMENTS. 

1. Heat a piece of tarnished copper wire in the upper part of 
the Bunsen flame. Note the change from cuprous to cupric 
oxide. When the wire glows drop it immediately into a test 
tube of methyl alcohol. What is the odor observed? Note the 
appearance of the copper. Complete the reaction : CH3OH -|- 
CuO«-^ 

2. Heat small pieces of clean and tarnished copper in the 
reagents described in experiment (i), p. 47. Finally pour off the 
liquids and add to each an excess of ammonia; a blue color 
shows the presence of copper. Have the pieces of copper been 
visibly affected? Write the reaction between CuCU and NH4OH. 

3. Compare the heat conductivity of copper and iron by hold- 
ing the ends of copper and iron wires of equal length and size 
in the Bunsen flame. 

' Aluminium, often called aluminum, is the most abun- 
dant of the elements, with the exception of O and Si. 
It is not found in the metallic state, but exists as sili- 
cates in various clays, in the topaz, garnets and feldspar ; 
as a hydrated phosphate in the turquoise; as an oxide 
in corundum, in the sapphire, ruby, emery, etc., and in 
bauxite, from which it is prepared commercially. 

The method of preparation consists in powdering the 
bauxite, freeing it from water and organic impurities, 
and heating it with caustic soda solution under high 
steam pressure. By the addition of alumina, aluminium 
oxide or alumina is then precipitated from the product 
in the form of a hydrate. The final process is the re- 
duction of alumina by electrolysis. A substance called 



. HOUS^HOIvD CHEMISTRY 53 

cryolite, which is a compound of aluminium, sodium 
and fluorine, melts at a low temperature and easily dis- 
solves alumina. A molten mixture of the two is con- 
nected with one terminal of an electric generator, and 
the current is introduced into the mass by means of a 
number of carbon rods dipping below the surface. De- 
composition by electrolysis results, and the aluminium 
collects in molten form at the bottom of the mass, from 
whence it is drawn off. The reaction taking place is usu- 
ally expressed as : 

2AI2O3 + 3C 1-^ 4AI + 3CO2. 

Properties. — Aluminium is silver-white in color, almost 
as hard and tenacious as steel, and ranks next to copper 
as a conductor of heat and electricity. It can be drawn 
to extremely fine wire and beaten to a film ^/4oooo of an 
inch in thickness. A film of oxide which forms on its 
surface is protective. Its specific gravity is only 2.6, and 
its melting point 600-700°. 

Aluminium is readily reactive with alkalies and hy- 
drochloric acid, and slightly so with organic acids, an 
action which is increased if sodium chloride is present 
or if the metal is tarnished. On account of its lightness 
it is much in demand for cooking utensils, but care must 
be taken that it does not come in contact with caustic 
alkalies. It discolors readily, and should be cleaned with 
a neutral scouring powder, or neutral soap and ammonia. 
Oxalic acid in hot dilute solution will remove any dis- 
coloration but will soon roughen the surface of the 
metal. 



54 HOUSEHOLD CHEMISTRY 

Several alloys of aluminium are known, the principal 
ones being bronzes. The true aluminium bronzes are 
compounds of Cu and Al alone, but various other metals 
such as Zn, Ni, and Mg, are also introduced. Aluminium 
has been added to brass with good effect. Other alloys 
are combinations with Fe, Bi, Sn and Ag. Magnalium is 
a useful alloy containing from 2 per cent, to 10 per cent, 
of magnesium. It takes a high polish and works well in 
the lathe. 

An alloy of aluminium and copper, called cupror, has 
been placed on the market recently. It is designed to 
take the place of silver for flat tableware, trays, bowls, 
pitchers, etc. The color of the alloy is that of i8-karat 
gold. The properties claimed for the new alloy are a 
high degree of polish, freedom from oxidation, resistance 
to acids, durability and cheapness. Articles made of it 
cost a little less than the best silver plated ware. 

Aluminium is of two forms in cooking utensils: cast, 
and rolled or spun. In the former, copper is added and 
the utensil is cast in one piece. The spun articles are 
made from sheets of aluminium rolled to the required 
thickness and drawn to the desired shape on a machine. 

EXPERIMENT. 

Test bright and tarnished aluminium as in experiment (i), p. 
47. Filter. Neutralize the acid solutions with ammonia in the 
presence of ammonium chloride and the alkaline solutions with 
HCl. Note the precipitates and write the reactions. 

Silver is found native with copper and gold, and also 
as a sulphide, associated chiefly with galena (lead sul- 



HOUSEHOLD CHEMISTRY 55 

phide). Small amounts are obtained from antimony and 
arsenic compounds, and in the form of silver chloride. 

In the electrolytic refining of copper (p. 51) silver is 
separated from the bath. The principal methods of ex- 
tracting silver from its ores are (i) amalgamation; (2) 
lixiviation ; (3) smelting. 

In the amalgamation process the chloride, bromide, 
etc., are brought into prolonged contact with mercury, 
which reduces the silver from its compound and forms 
an amalgam with it. Complex sulphides of silver resist 
amalgamation and must have a preliminary treatment 
consisting in roasting the ore with common salt or with 
copper compounds to produce silver chloride. This was 
the patio process used in Mexico for 350 years, and only 
recently superseded by the cyanide process, described 
under lixiviation. 

In the lixiviation processes the silver is dissolved 
from its ores by aqueous solutions and is precipitated as 
the metal or as a sulphide. The cyanide method is the 
most important. It is a complicated process. In brief, 
the ore is crushed fine, mixed with cyanide solution, and 
the pulp kept in contact with the solution until the dis- 
solution of the silver is complete. The mass then passes 
into vacuum filters, and silver is precipitated from the 
clear filtrate by either zinc dust or zinc shavings. Smelt- 
ing with nitre follows. The silver thus produced is im- 
pure, and is carried through a refining process. 

Smelting is a process applied to silver ores containing 
large percentages of lead and copper. From the blast 
furnace the silver comes out associated with lead as pig 



56 HOUSEHOIvD CHEMISTRY 

lead or "base bullion." The amount of silver is seldom 
over 2 per cent. It is separated from the lead by the 
process of zinc desilverization and cupellation. Zinc 
and lead are quite insoluble in each other and silver is 
more soluble in zinc than in lead. Taking advantage of 
these facts, the process is operated as follows : silver lead 
is melted in large cast iron kettles and the zinc added and 
well stirred. On standing and partially cooling, the zinc, 
carrying silver and a little lead, rises and forms a crust 
which is skimmed and heated in retorts to drive off zinc. 
The residue, lead and silver, is then heated in a rever- 
beratory furnace (cupellation) with bone ash bed. The 
lead oxidizes, melts and is absorbed by the bone ash, 
leaving the silver. 

Properties. — Silver is a white metal, softer than copper 
and harder than gold. It is highly ductile and malleable, 
and the best conductor known of heat and electricity. 
Its specific gravity when cast is 10.5, and its melting 
point about 960°. It does not oxidize readily in air, but 
is rapidly attacked by sulphides, producing a black coat- 
ing of AggS. 

Oxidized silver is made by dipping silver articles in a 
solution of potassium hydrogen sulphide, which produces 
a film of silver sulphide. 

Silver dissolves readily in nitric acid, is somewhat re- 
active with most other mineral and organic acids, but 
not at all with alkalies. 

In order to harden silver, it is alloyed with copper in 
the following proportions: coin silver, 900 parts silver, 



HOUSEHOI.D CHEMISTRY 57 

100 parts copper ; sterling silver, 925 parts silver, 75 parts 
copper. All solid household silver is now "sterling." 

Many silver ornaments contain even less silver, but 
articles stamped "sterling" are trustworthy. Silver 
plated ware consists of articles fashioned of German 
silver or pewter, on which is deposited by electrolysis a 
triple or quadruple coating of pure silver. The process 
is similar to copper plating, the silver bath consisting of 
potassium silver cyanide, KAg(CN)2. The coating has a 
frosted appearance and needs burnishing or smoothing 
before use. Since the coat deposited in this manner is 
pure silver, these articles do not stand as much careless 
and rough handling as the harder sterling or coin ware, 
and much of the coating is rubbed off in the process of 
cleansing with the so-called silver polishes. Plated ware 
will last much longer if simply washed with hot water 
and neutral soap. In order to remove the tarnish due to 
sulphides (eggs), soak the articles in a clean tin or 
aluminium pan containing enough baking soda solution 
to cover and let them remain until bright. The soda 
solution is made by dissolving a tablespoonful of 
NaHCOg in a quart of tepid water. Or the water may 
be made to boil over the silver and the soda added. 

Tin, (Stannum) Sn, occurs in Cornwall, Wales, and 
the East Indies as Cassiterite (tin stone), SnOg. The 
ore is crushed and washed to remove rock, roasted to 
oxidize sulphide of iron and copper and to remove arse- 
nic, then leached with water to dissolve sulphate of iron 
and copper, dried and reduced with coal in a reverbera- 
tory furnace. 



58 HOUSEHOIvD CHEMISTRY 

Properties. — Tin is a soft, silver-white, crystalline 
metal, malleable but not tenacious. It melts at about 
230°. Its specific gravity is 7.3. On bending bar tin a 
peculiar crackling sound, called the "cry of tin," is 
heard, caused by the friction of interlaced crystals. 
Pure tin resists oxidation in moist air, and is not quickly 
susceptible to the action of dilute acids and alkalies. 
However, there are certain fruits and vegetables which 
attack the coating of a tin can to some extent, forming 
salts of tin which are objectionable. A lacquered can is 
preferable for raspberries, cherries, plums, beets, pump- 
kin, hominy, etc. On the other hand, cases of poisoning 
traced to canned foodstuffs may have been caused either 
by the imperfect condition of the food when canned or 
by careless soldering. The latter evil is now largely done 
away with by present methods of sealing tin cans. 

Tin plate is made by dipping carefully cleaned sheets 
of iron or steel in molten tin. It is much used for roof- 
ing, household ware and cans for preserving food. Care 
must always be exercised that tin vessels are not over- 
heated, since the element has a low fusion point and will 
run off leaving the iron bare, therefore it should never 
be used in the oven or for broiling, roasting or frying. 
Liquid mixtures may be cooked in tin vessels without 
doing any damage. 

Various useful alloys are known, viz., bronze, soft 
solder (half tin, half lead) ; plate pewter, antimony, bis- 
muth and copper; Britannia metal, 10 per cent, antimony. 



HOUSEHOLD CHEMISTRY 59 

EXPERIMENTS. 

1. Heat a small piece of tin plate over the Bunsen flame, note 
the crystalline appearance on cooling; treat a piece with mod- 
erately strong acid and note a similar effect. Where have you 
frequently seen this phenomenon? 

2. Subject pieces of bright and tarnished tin to the action of 
dilute acids and alkali as under iron. Test the filtered liquids 
for soluble tin compounds by acidifying with HCl and adding 
mercuric chloride. A white precipitate of mercurous chloride 
results, passing to a gray precipitate of metallic mercury, if 
sufficient stannous chloride is present, the tin acting as a reduc- 
ing agent as follows : 

SnClj +2HgCl2 -^ SnCl^ -f-2HgCl, 
2HgCl + SnCl2 «^ SnCl^ +Hg2. 

Write the reactions for the action of HCl, CH3COOH and 
NaOH on tin. (NaOH produces sodium metastannate as the 
final product.) 

Lead, Pb (Plumbum), occurs principally as galena, 
PbS (frequently carrying silver). The metal is obtained 
by roasting the ore until partially converted into oxide 
and sulphate. On closing the furnace doors and increas- 
ing the heat, the charge is reduced to metal : 

PbS + 2PbO »- 3Pb + SO2. 
PbS + PbSO, «- 2Pb + 2SO2. 

Lead is gray in color, soft, of slight tensile strength but 
very malleable. Melting point 325°-335° and specific 
gravity about 11.3. It is only slightly soluble in acids and 
alkalies, but its oxide is very soluble. Lead pipes are 
formed by forcing warm lead through steel dies by 
hydraulic pressure. They are largely used for conduct- 
5 



6o HOUSEHOI^D CHEMISTRY 

ing water in the household. The danger of drinking 
water conducted by lead pipes is much exaggerated. 
Unless the water is unusually soft, the interior of the 
pipe quickly becomes coated with insoluble sulphate and 
carbonate. A wise precaution with new plumbing is to 
allow the water to run for some minutes before use. 
lycad enters into many useful alloys previously men- 
tioned. 

lycad oxidizes superficially, the compound formed 
being the black suboxide, PbgO, formerly used in place 
of graphite for lead pencils. 

The crystalline character of lead and some of its com- 
pounds can be shown by the following : 

EXPERIMENTS. 

1. Dissolve two small portions of lead oxide, one in dilute 
HNO3 and the other in acetic acid; pour a little of each solution 
in two separate watch-glasses and set them aside to evaporate. 
Examine the crystalUne residue in each case. Scrape two pieces 
of lead bright and immerse one in strong nitric acid, the other 
in acetic acid; allow them to stand several days, then examine, 
and compare with the crystals found above. 

2. Immerse bright lead in water charged with carbon dioxide; 
after several hours' standing pour off the water and test it with 
hydrogen sulphide. 

3. Treat small pieces of bright and tarnished lead separately 
in weak solutions of acids and alkali as under iron. Pour off 
the clear solutions, acidify with HNO3 where necessary, and 
test for lead by passing H2S through the liquid. A black pre- 
cipitate (PbS) indicates lead. 

Summary. — Each student should make a tabular state- 
ment comparing the metals of the household with regard 
to action with acids and alkalies, cost, durability, sus- 



HOUSEHOI^D CHEMISTRY 



6l 



ceptibility to oxidation, methods of cleaning, heat prop- 
erties, etc. 

USSFUI, TABIyES. 



Silver. 

Copper. . - . . 
Aluminium 

Brass 

Zinc 

Tin 

Nickel 

Iron 

Steel 

Platinum . . 
Porcelain • . 
Soapstone- • 

Glass 

Asbestos • . • 



Heat conductivity 



lOO.O 


0.056 


73-0 


0.094 


48.0 


0.218 


23.0 


0.086 


19.0 


0.093 


i5'0 


0.055 


14.0 


0.109 


11.9 


0.II5 


11.6 


0.II7 


8.4 


0.032 


0.24 


0.2 


0.2 


0.2 


0.16 


0.2 


O.OOI 


0.194 



specific heat 



CHAPTER V. 



GLASS, POTTERY, AND PORCELAIN. 

These materials belong to a series of infusible and 
insoluble silicates of great utility in all household opera- 
tions. Glass consists of a mixture of silicates in the 
amorphous state and is highly prized on account of its 
brilliancy and transparency; the mass may be colored 
without affecting either of these qualities. The usual 
varieties of glass consist of a mixture of alkaline (with 
alkaline earth) or heavy metal silicates, and are known 
as Bohemian, Crown, Bottle and Flint glasses. 

Bohemian glass is a silicate of potash and lime. It is 
very infusible and insoluble, therefore especially adapted 
for chemical purposes. 

Window or Crown glass is a silicate of soda and lime. 
It is more fusible but harder than the Bohemian and is 
more easily affected by acids. 

Bottle glass is an impure variety of the above, colored 
with iron. 

Flint glass is a potash lead silicate. This is the most 
fusible kind of glass and is easily attacked by chemical 
reagents; on account of its high refractive power, it is 
much used for optical purposes. 

All kinds of glass are prepared by fusing more or less 
pure silica in the form of sand or powdered quartz with 
the potash or soda and lime or red lead, for many hours 
in large earthenware pots, heated in appropriate fur- 
naces. When the mass has cleared, it is cast or blown 
and cooled rapidly in order to retain its transparency. 



HOUS^HOI^D CHEMISTRY 6^ 

Annealing is a process of heating to a temperature 
short of softening and cooling slowly, thereby reducing 
the brittleness. 

While transparency is a very important property of all 
glasses, there are several useful opaque forms. Opaque 
glass is the result of suspending finely divided infusible 
material in the molten mass. Such materials are bone 
phosphates, cryolite, zinc or tin oxides, etc. The enamels 
used on cooking utensils are of similar composition, and 
should be handled with the same care as glass articles. 
On account of the great difference in the expansion co- 
efficients of the glaze and metal base, too sudden cooling 
or heating of the utensil should be avoided. lyikewise 
judgment and care should be exercised in the selection 
and use of cleansing agents. Pure neutral soap is the 
best medium to employ, and under no circumstances is 
the use of strong caustic alkalies or sharp abrasives jus- 
tified. 

One of the most characteristic properties of all glasses 
is the solvent effect of hydrofluoric acid and soluble 
fluorides. Etching on glass is largely accomplished by 
this means. 

Colored glass is the result of dissolving some appro- 
priate mineral oxide in either variety of glass : 

Ruby — oxide of gold or copper. 

Topaz — sulphide of antimony. 

Yellow — silver chloride or borate. 

Green — oxide of chromium. 

Blue — oxide of cobalt. 

Amethyst — oxide of manganese. 



64 HOUSEHOLD CHEMISTRY 

EXPERIMENTS. 

1. Corrosive Action of Alkalies — Half fill common prescription 
bottles (4 oz.) with strong caustic soda solution. Place them in 
warm salt water, bring slowly to a boil and continue for at 
least I hour, then cool slowly, pour out the contents, rinse with 
clean water and examine the inner surface. 

2. Etching Tests — (a) With a clean steel pen and dilute hydro- 
fluoric acid, HF, write your name and the date on a clean 
microscope slide. 

(b) Thinly cover a clean watch-glass with warm paraffin. 
When cool cut your name with a pencil point through the paraf- 
fin and immediately invert over a lead dish containing a mixture 
of fluorspar and concentrated sulphuric acid. After half an 
hour's gentle heating, rub off the paraffin and examine the 
result. 

3. Detection of Arsenic, Lead, Etc — Fuse finely ground chips 
of kitchen utensil enamel with an excess of potassium sodium 
carbonate in an iron or nickel crucible, cool and extract the 
melt with hot water. Filter and wash with residue several times 
with hot water. Test the filtrate for arsenic, lead, and acids, 
by dividing it into 3 parts — two of one-quarter each and the third 
the remaining half. 

Part I. Test for arsenic by making strongly acid with HCl 
and boiling with a strip of clean copper. A gray or black coat- 
ing indicates arsenic. 

Part II. Make acid with HCl and pass H2S rapidly through 
the solution. A black precipitate indicates lead. 

Part III. One-half of the solution — test for sulphates, borates, 
phosphates, and silicates, as follows: 

Neutralize with HCl ; if any precipitate forms, filter and divide 
the filtrate into 3 parts. The residue is silicates. Take i part 
of the filtrate, thoroughly moisten a strip of turmeric paper with 
it and dry at 100° C. A pink color indicates borates. 

To another part, add barium chloride and a few drops of HCl. 
A white crystalline precipitate indicates sulphates. Pour a few 



HOUSKHOI^D CHEMISTRY 65 

drops of the remaining part into an excess of ammonium molyb- 
date. Warm gently and a yellow color or yellow crystalline 
precipitate indicates phosphate. 

Porcelain and Pottery are fused silicates of alumina, 
the former pure, and the latter contaminated with oxides 
of iron^ manganese, etc. 

The primary source of these wares is clay, a highly 
infusible hydrated silicate of alumina. For porcelain 
making it is mixed with some fusible silicate such as 
feldspar, and a small quantity of water, moulded into 
shape, dried and heated in a furnace for many hours. 
The feldspar or flux only melts and running through the 
porous mass cements it together. Even after firing, the 
ware requires coating with the glaze, a mixture of 
slightly fusible material suspended in water into which 
the article is dipped. It is dried and returned to the fur- 
nace for heating. The glaze is, in effect, a true glass and 
makes the mass impenetrable to liquids. Decorative 
effects are produced in two ways, called under- and over- 
glaze, of which the former is the better and more per- 
manent. For under-glaze work, finely ground colored 
glass suspended in turpentine is applied to the unglazed 
ware and afterwards ''fired" at the high temperature of 
the porcelain furnace. The glaze is subsequently applied 
and fired as before. Over-glaze decoration admits of 
the use of colors which may be injured by the high heat 
of the porcelain furnace and is applied at a lower tem- 
perature in a muffle. The colors consist of various 
oxides mixed with borax, litharge, nitre, etc. They are 
applied in watery solution. 



(£ HOUSEHOI^D CHEMISTRY 

Stoneware is an impure form of porcelain, somewhat 
more fusible and usually glazed with borax. The finer 
qualities are known as china. Earthenware and brick 
consist of clay and sand, mixed with water, moulded, 
dried and fired in a kiln. The former is usually glazed 
with salt, while the latter is left in the porous state. 

Since most of our decorated table china is over-glaze 
ware it is likely that it will not successfully withstand 
repeated washings, especially since modern practice has 
brought into use many forms of alkaline detergents, i. e., 
soap powders and cleaners. Some of these contain 
bleaching agents, which liberate chlorine and are there- 
fore destructive to gold, but prolonged contact with the 
strong alkalies in their composition is sufficient to hasten 
the removal of both gold and color decoration. 

EXPERIMENTS. 

1. Heat several decorated dishes in new enameled saucepans 
with solutions of various soaps and other cleansers. Keep the 
pans covered and boil gently for i hour. Cool, rinse in clear 
water, and examine the effect, both on the china and the sauce- 
pan. 

2. Porosity — Weigh small pieces of dry unglazed porcelain 
and earthenware, soak over night in water, wipe dry and weigh 
again. Calculate the per cent, of water absorbed. 

3. Fusibility — Heat small splinters of porcelain and earthen- 
ware held in platinum wire (spiral) at the highest heat of your 
burner. Cool and examine with a magnifier. Are the edges 
sharp or rounded? 

4. Testing for Lead in the Glaze — Boil the article for some 
time in caustic soda, cool the liquid and add (NH4)2S. A dark- 
ening of the liquid or a black precipitate due to lead sulphide, 
PbS, indicates lead. 



CHAPTER VI. 



FUELS. 

Fuels are materials used for producing heat; they 
must be capable of uniting with oxygen under easily 
obtainable conditions and of evolving much heat energy 
during the process of combustion. Occurring as gases, 
liquids and solids, carbon and its compounds largely fill 
the required conditions. 



Classification. — A logical 
would result as follows : 



arrangement of the fuels 



f Natural 



r Hydrogen 



Pure fuels 



l^ Hydrocarbons 

Carbon 
monoxide 

Hydrocarbons 
Hydrocarbons 
r Alcohols 
\ Hydrocarbons 
Anthracite 
Coke 
Charcoal 

Soft coal 
' Peat 
Woods 

Coals, petroleum and natural gas are evidently of plant 
and animal origin, produced by a natural method of 
decomposition, similar to a process of dry distillation. 

The terms pure and impure are used in a restricted 
sense, the former signifying that the substance is ready 
for direct combustion while in the latter case a number 
of complicated chemical changes must take place before 



Impure fuels 



Gases 



Liquids 



Solids 



Solids 



"I 

I Artificial 

{Natural 
Artificial 

r Natural 

< 

L Artificial 



Natural 



68 HOUSEHOI^D CHEMISTRY 

combustion is possible. This is explained in detail in 
the discussion of the composition of wood. 

Historical: Woods both hard and soft and charcoal 
have been used from the earliest times. Peat, a form of 
partly carbonized turf, was the main fuel of European 
countries during the Middle Ages and is still in use. 
Soft coal came into use during the 15th century, while 
gas and hard coal were first employed in the early part 
of the 19th century, and hydrocarbons about the middle 
of the same epoch. Alcohol is just coming into gen- 
eral use in our own times. 

Impure solid fuels on account of more extended use 
will be first discussed. 

Wood, peat and soft coal are such impure forms of 
fuel and must undergo so many and such complicated 
chemical changes before they are capable of yielding 
heat, that their actual fuel value is frequently over-esti- 
mated and rarely understood by the consumer. The fol- 
lowing is a brief and simple statement of composition 
and changes to be expected: 

Wood contains, moisture, (HjO); resin, (C^H;^); 
starch, gum, and cellulose, n (CJI^fi^); oil, (C^^H^O^); 
mineral matter or ash. 

Considerable heat is required to drive off the mois- 
ture and raise the starch, cellulose, etc., to such tempera- 
tures that they will decompose, yielding gases of a com- 
bustible nature, for example CO, CH4, C2H4, C2H2, H2 ; 
in this decomposition H2O is formed and must be driven 
off as a gas. Much heat is also absorbed by the ash in 
forming new chemical compounds. In fact the fuel effi- 



HOUSEHOLD CHEMISTRY 69 

ciency of wood depends entirely upon the relative vol- 
umes of combustible gas and charcoal furnished, and 
as the charcoal or carbon is the best solid fuel, the wood 
furnishing the largest proportion of carbon in this form 
is the best fuel, hence we find it advantageous to use 
hard wood. It must be understood that carbon or char- 
coal at a red heat combines with a limited amount of 
oxygen and forms a combustible gas, carbon monoxide, 
CO, a fuel of the highest heating efficiency. 

Soft coal, a partly carbonized plant product, produces 
less water by chemical change and yields the combustible 
gases and carbon (coke) in larger proportion. 

Hard coal is superior to soft, since it is a purer form 
of carbon and yields very little combustible gas. 

EXPERIMENT. 

To determine the value of coal or wood for fuel purposes, 
proceed as follows : Take i gram of pulverized coal or small 
pieces of wood in a weighed crucible, dry at 120° with cover 
off, cool and weigh; the loss is water. Heat the crucible with 
cover on in a strong Bunsen flame for 7 minutes, cool and weigh ; 
the loss is volatile combustible matter (tar, smoke, etc.). Heat 
again with cover off until nothing remains but ash. This opera- 
tion will require some time; cool and weigh; the loss is fixed 
carbon (actual fuel). Subtract the weight of the crucible; the 
difference is ash. 

The quantity of ash in coals is always greater than in 
wood, owing to the presence of foreign mineral sub- 
stances such as silica, lime and sulphide of iron derived 
from the earthy strata in which the coal is deposited. 

Flue dust, collecting in stove pipes and flues where 
hard coal is burned, contains sulphate of ammonia. 



70 house:hoi:.d chemistry 

When cool, this salt absorbs water and attacks iron, 
rapidly corroding the pipes. This fact explains the neces- 
sity of cleaning the smoke pipes of furnaces and stoves 
in the spring of the year when the heating apparatus is 
no longer used. 

EXPERIMENT. 

Collect some of the light gray dust from a smoke pipe, treat 
about I gram with boiling water on a filter, pouring the liquid 
through several times. Reserve the residue and test the liquid 
in the usual manner for ammonia and sulphates. Extract the 
residue still on the filter-paper with boiling dilute HCl until 
the residue is light in color. This is mainly silica from the 
coal ash. Test the acid filtrate for ferric iron and lime in the 
usual manner. 

Liquid Fuels. — These comprise alcohols, and hydro- 
carbons in the form of gasoline or naphtha, and kero- 
sene. The hydrocarbons are highly inflammable liquids 
obtained from crude petroleum. 

The distillation of petroleum was carried on in Europe 
early in the i8th century, and there is evidence of the 
use of the crude oil by fire worshippers as far back as 
Zoroaster. The great oil region of Europe is the Baku 
peninsula on the Caspian Sea. Crude petroleum was 
known to the Indians in America, and in New York 
State it became popular as a specific for rheumatism, 
under the name of Seneca Oil. Refined petroleum in 
the United States dates from 1855, when it was distilled 
and put on the market as a patent medicine called Amer- 
ican Oil. Up to this time a limited quantity had been 
obtained at or near the surface of the ground. In 1859, 
in Titusville, Pa., Col. Drake applied the method of 



HOUSEHOI^D CHEMISTRY ^I 

boring artesian wells to obtain petroleum from under- 
lying strata, and the industry was revolutionized. In 
that year 2,000 barrels of crude petroleum were produced, 
2 years later 2,000,000, and in 1910 210,000,000 barrels. 
The new supply gave a material more profitable for refin- 
ing than shale oil. By fractional distillation at first, a 
number of distillates were obtained ranging from petro- 
leum ether, naphthas, gasoline, etc., to solid paraffins. 
The yield of gasoline by this process was entirely insuffi- 
cient, however, to meet the sudden demand created by 
the automobile and motor engines, so a system of "crack- 
ing" was devised, which has greatly increased the light 
oil distillate and is better suited to the refining of oils 
from the newer western fields. 

Cracking Process. — This is a method of distilling at a 
temperature higher than the normal boiling points of 
the constituents to be obtained, which effects a dissocia- 
tion of many of the heavier oils into lighter hydrocar- 
bons. As the process is conducted in some places, the 
charge of oil (about 1,000 barrels) is put into a side- 
firing still, the temperature is raised to 600° or 700° F., 
and the vapors as they come off are carried to a series 
of condensers, where they are separated, the heaviest 
vapors condensing first, the lightest traveling farthest 
before being condensed. The vapors of a considerable 
amount of the oil intermediate between kerosene and 
lubricating oils are returned to the still, superheated, and 
decomposed, so increasing the yield of light distillate. 
Usually 3 streams of oil of different specific gravities 
are simultaneously received : the heaviest, or the paraffin 



72 house:hoi.d chemistry 

oil distillate; the intermediate, or gas oil, and the light 
oil distillate. The paraffin oil distillate is worked up 
to produce lubricating oils, paraffin, etc., the interme- 
diate distillate is refined for burning and gas oils, and the 
light distillate is fractionally distilled and yields a num- 
ber of important compounds, such as : 

Cymogene, specific gravity iio° Baume. Used in the 
manufacture of ice. 

Rhigolene, specific gravity ioo° Baume. Used as an 
anaesthetic. 

Petroleum ether, 85^-80*^ Baume. Used as a solvent 
and for carbureting air in gas machines. 

Benzine, 89^-82° Baume. A solvent. 

Gasoline. Varies widely in specific gravity and qual- 
ity, according to the demand. It may have a specific 
gravity of 80° -60° Baume. 

' For the purification of petroleum products the use of 
sulphuric acid followed by soda lye is universal. Aro- 
matic hydrocarbons, fatty and other acids, phenols and 
tarry bodies are thus decomposed or removed. Sulphur 
compounds are taken out in the form of sulphides by 
copper. 

Chemical Nature of Petroleums. — Crude petroleum from 
different fields shows great differences in chemical con- 
stituents. The Pennsylvania petroleum yields hydro- 
carbons of the methane series principally, compounds 
from C4H10 to C35H72 having been isolated in almost 
unbroken sequence, with many of their isomeric forms. 
Ring hydrocarbons such as benzene, CqRq, have also 
been found in smaller quantity. 



housh:hold che:mistry 73 

The California oils are of varied character and con- 
sist of a more or less dense asphaltic base. Asphalt is 
usually regarded as evaporated and oxidized petroleum. 
Phenols are common constituents; nitrogenous ring 
compounds and the olefines from C2H4 to CgoHgo in- 
clusive have been obtained. The California field is very 
active, a single well having made a record of 30,000 to 
60,000 barrels per day. 

The Texas oil seems to combine the characteristics of 
the Pennsylvania and the California types, while the mid- 
western field produces both kinds. 

Russian and Cuban petroleum consist largely of the 
unsaturated hydrocarbons of the naphthene series, 

C„H2«_6 -\- tlfi' 

The depth at which petroleum is found is of interest. 
In Pennsylvania wells range from 300 to 3,700 feet; in 
California they have been drilled to a depth of over 
4,000 feet. 

Products of Combustion. — At temperatures slightly 
above normal liquid fuels readily combine with oxygen, 
producing intense heat and yielding water and carbon 
dioxide as products but no ash; with too small supply 
of oxygen the temperature of combustion is much low- 
ered and a large part of the carbon is not consumed and 
escapes in a free state, producing a yellow flame and if 
in great excess much black smoke — a very familiar phe- 
nomenon in kerosene lamps. 

With great excess of oxygen, as when the hot vapor 
of these liquids is mixed with many times its volume 



74 house:hoi.d chemistry 

of air, in a confined space, the combustion is so rapid 
as to produce an explosion (automobile engine). When 
using these products for fuel purposes care must be 
taken that these last conditions do not exist. Hence as a 
measure of safety the lamp or stove reservoir is kept 
well filled and cool. The following simple experiments 
will serve to impress these important facts on the 
student's mind > — 

EXPERIMENTS. 

1. Pour not more than i or 2 drops of clear gasoline into a 
clean, dry, wide-mouth bottle of 12 to 16 ounces capacity, stir 
the vapor for a moment with a hot glass or iron rod and bring 
a lighted match over the mouth of the bottle; a slight but per- 
ceptible explosion should result with or without blue flame. 

2. Pour a teaspoonful of the same liquid in a shallow porcelain 
dish or saucer, apply the lighted match and note the yellow 
flame, but no explosion. Quench by covering with cloth, stiff 
cardboard or any article that will exclude air. 

Gasoline is used quite largely in some localities as a 
source of heat, being consumed in the so-called blue 
flame stove, which operates by heating the liquid to such 
a temperature, air being excluded, that vapor forms rap- 
idly and under slight pressure. It is then conducted to 
the burner (Bunsen), mixed with the proper amount of 
air, and burns with a blue flame. These stoves and 
heaters are perfectly safe as long as they are kept clean, 
do not leak liquid, are kept well filled and furnished 
with good gasoline. The quality of gasoline may be 
determined by the following tests : 

1. Observe the color; it should be white as water. 

2. Clearness; if cloudy, dirt or water is present. Evaporate 



house:hoi.d chemistry 75 

a small quantity in a clean porcelain dish over warm water (no 
flame) and examine the residue; also filter some through clean 
dry chamois skin. Water and dirt will remain on the skin. It 
is a wise precaution for users of gasoline for any purpose to 
filter as above before using. 

3. Test with dehcate litmus paper; it should be neutral. 

4. Determine the specific gravity with the Baume hydrometer 
for light liquids; it should register not higher than 62° for fuel 
purposes. 

Kerosene, erroneously called an oil, is much more 
extensively used and widely known; it is probably the 
cheapest and best liquid illuminating agent of the present 
day. The ordinary kerosene wick lamp is so well known 
as to need no explanation. Kerosene, however, is used 
in blue flame stoves, such as the Khotal, etc., and al- 
though more troublesome to manipulate is preferred by 
most people because the danger is minimized. 

Kerosene should successfully stand tests i, 2, 3, given 
under gasoline. The specific gravity should be 48° 
Baume. 

In addition, flash and fire tests are prescribed in most 
parts of the world. The former signifies the temper- 
ature at which the oil gives off ignitable vapor, and the 
latter the point at which it takes fire. The experiment 
below represents the open-cup method of determining 
the flash point, the figures of which are always slightly 
lower than by other methods : 

Half fill a 200 cc. beaker with kerosene, place over warm 

water, stir gently with an accurate Fahrenheit thermometer and 

heat slowly not more than 2° rise per minute, until a small open 

flame brought over the surface of the liquid causes a blue flame 

6 



76 HOUSEHOLD CHEMISTRY 

and slight explosion. Note the temperature; it is the flash point 
and should not be lower than ioo° F. Air currents and draughts 
should be excluded in this experiment. 

Kerosene and gasoline are unsaponifiable. Prove this 
in the case of kerosene by the following : 

Heat a small quantity of kerosene with one-seventh its volume 
of a solution of sodium hydroxide (38° Baume) over hot water, 
stirring often. On cooling, does the product resemble soap? 
Is kerosene rightly called an oil? 

The increased efficiency of kerosene as a burning fluid 
in recent years is partly due to the presence in its com- 
position of unsaturated hydrocarbons, formed during 
the cracking process. These have a higher illuminating 
power than the former saturated type found in the oil. 

Alcohols. — Of this series, only methyl or wood alcohol 
and ethyl or grain alcohol are used as fuels. A mixture 
of the two (90 parts ethyl, 9 parts methyl -j- i part ben- 
zine) has come into general use under the name of de- 
natured alcohol; it is essentially ethyl alcohol. Methyl 
alcohol, CH3OH, is produced commercially by the dry 
distillation of wood and is known as pyroligneous or 
wood spirit ; it contains light wood tar, acetone, and acetic 
acid, which should be completely removed before using, 
leaving a bland mild-smelling liquid similar to ethyl alco- 
hol, known as Columbian Spirit. Much of the ordinary 
wood alcohol is quite impure. Tar and acetone are easily 
distinguished by the color and odor, especially if gently 
heated; acid is readily shown by litmus paper. 

As a burning fluid methyl alcohol is distinctly inferior 
to grain alcohol. The following equation shows the 



HOUSEHOLD CHEMISTRY 7/ 

chemical change during complete oxidation: 2CH3OH 
+ 3O, — 4H,0 + 2CO,. 

In stoves or lamps of the best type, ethyl or grain 
alcohol burns as follows : 

C,H,OH + 3O, -> 2CO, + 3H,0. 

Comparing this equation with that of methyl alcohol 
it will be seen that the amount of CO2 is doubled, hence 
it is fair to assume that the heating effect is greater; 
ethyl alcohol is less volatile than methyl, therefore loss 
by evaporation during use is less. 

Methyl alcohol is readily oxidized to formaldehyde by 
means of hot copper oxide (see Experiment i, p. 52). 
This serves as a test for the identification of this alcohol. 
By further oxidation methyl alcohol yields formic acid: 

CH,OH 4- O, —- HCOOH + H,0. 

Ethyl or grain alcohol, CgHgOH, is prepared by the 
fermentation of glucose or maltose by means of yeasts 
and distillation of the product. It is a colorless liquid 
with pleasant and characteristic odor, usually containing 
about 95 per cent, of pure alcohol and the balance water 
and small amounts of impurities, acetic acid and acetone 
more especially; these are not particularly objectionable 
if the liquid is to be used for generating heat or general 
solvent purposes, but in many chemical operations 
further purification is necessary. Pure alcohol, free 
from aldehyde and acid for chemical purposes, can easily 
be made from the ordinary 95 per cent, variety or even 
waste alcohol by allowing it to remain for several days 



78 HOUSEHOLD CHEMISTRY 

in contact with slightly rancid tallow or grease and sub- 
sequently filtering, distilling and neutralizing the product. 
On account of the high price, due to the government 
tax, ethyl alcohol was formerly little used for heat and 
power purposes, but since the introduction of denatured 
alcohol, the cost has fallen and the use enormously 
increased. At the present price, it is somewhat more 
expensive to use than gasoline but far safer and pleas- 
anter to handle. 

EXPERIMENTS. 

1. Determine the boiling point of 95 per cent, ethyl alcohol by 
distilling 100 cc, in a small flask fitted with a thermometer and 
condenser. 

2. Determine the specific gravity of alcohol by means of the 
hydrometer and check the result by the Westphal balance. 

3. Ethyl alcohol combines with iodine in the presence of strong 
alkali, forming iodoform : 

C2H5OH + 4I2 + NagCOg 1^- 2 CHI3 + CO2 + 2NaI + 2H2O. 

To 3 cc. of C2H5OH and an equal amount of tincture of iodine 
in a test tube, add NaaCOg in small amounts, shaking after each 
addition and warming gently until the solution is just decolorized 
and yellow crystals of iodoform appear. About 5 cc. of NasCOs 
will be used. 

4. By the use of an oxidizing agent such as KaCraO?, ethyl 
alcohol is converted into acetaldehyde : 

3C2H5OH + KgCfaOT + 4H2SOi «^ 

3CH3CHO + K2SO, + Cr2(SO,)3 + 7H2O. 
Heat 10 cc. of alcohol with i cc. of KzCrjOi solution acidified 
with sulphuric acid, notice the reduction of the chromium to 
base and the odor of aldehyde. 

5. Since ethyl alcohol oxidizes readily to acetic acid, some 
acidity is found in most samples. The amount may be such as 



HOUSEHOLD CHEMISTRY 79 

to cause corrosion of metal containers or burners in alcohol 
stoves. 

Determine the acidity of lo cc. of alcohol with N/io alkali, 
calculating the percentage in terms of acetic acid. 

Gases. — Gas consisting of hydrogen, carbon monoxide, 
and various hydrocarbons is the ideal fuel. There are 
seven varieties in use for fuel and lighting purposes, vis. : 

Natural gas 
Water gas 
Coal gas 
Gases proper ^ Acetylene gas 

Blau gas 

(^ Pintsch gas 

f Cold air charged with naphtha 
Naphtha or air gas i 

^ I vapor. 

Natural gas has been found in large pockets in the 
earth in various localities for many years. The shrines 
of antiquity were in some cases supplied with gas from 
crevices in the earth; it is probable that the temple of 
Diana at Ephesus had a natural gas well. 

Fredonia, N. Y., was lighted with natural gas as early 
as 1825. The supply was accidentally discovered when 
boring for salt, as these earth pockets are reached by 
drilling as for oil or brine. The gas comes out under 
tremendous pressure, which must be controlled and re- 
duced for household use. Its main constituent is meth- 
ane or marsh gas, which has little or no illuminating 
power, but is an excellent source of heat. The supply 
of natural gas from earth pockets is gradually becoming 
exhausted. 

Three classes of natural gas are recognized : 



8o HOUSEHOI^D CHEMISTRY 

(i) The gas which issues from marshy beds, and 
contains methane as its only combustible constituent. 

(2) Natural gas found in pockets occurring in oil 
fields but not associated with oil. In this, methane pre- 
dominates, but hydrocarbons higher in the series are 
found. This is the gas which supplies Pittsburgh and 
Cleveland. 

(3) A gas associated with petroleum, called "wet" 
gas, from which gasoline can be obtained. Natural gas 
of this type is found in almost every oil-producing state 
of the Union. By compressing this gas to 350 pounds per 
square inch, and passing it through cooled condenser coils, 
a gasoline is produced with specific gravity of "JJ^ to 110° 
Baume. Being extremely volatile, it is kept in tanks 
under heavy pressure, and when drawn off is usually 
mixed at once with low grade refinery naphthas. The 
amount of gasoline obtained in the last few years from 
natural gas has approximated 10,000,000 gallons annually. 
The residual gas left after the gasoline extraction has a 
high heating value and is utilized for that purpose. 

Water Cras. — By passing steam at high pressure over 
incandescent carbon a mixture of hydrogen and carbon 
monoxide, known as water gas, is produced. The carbon 
used may be in the form of anthracite, coke or even 
charcoal. A high temperature is necessary for the 
operation, usually about 3,000° F. Decomposition takes 
place, the chemical change being as follows: 

2H,0 + C, --^ 2CO + 2H,. 
In order to give the resulting gases illuminating quality 
they are mixed with light hydrocarbons and the com- 



HOUSEHOIvD CHEMISTRY 8l 

bination passed through a red hot zone. The naphtha 
vapors are broken up (cracked) into permanent gases 
such as methane, ethylene and acetylene, giving the prod- 
uct a composition similar to coal gas (q-v.) but com- 
bined in somewhat different proportions. Since it con- 
tains more carbon monoxide it is generally regarded as a 
better fuel. 

Coal Gas. — From soft or bituminous coals, a gas can 
be produced by dry distillation. This was the first 
method used for making gas, and dates back to early 
days of the 19th century. On account of the many and 
valuable by-products produced, vis., ammonia, coal tar, 
carbolic acid, naphthalene, cyanides, etc., it will probably 
be used for many years to come. 

The process consists in heating the coal in large clay 
retorts, drawing off and cooling the gas in order to con- 
dense tar, washing to remove ammonia, tar, etc., remov- 
ing sulphur with lime or iron oxide, storing and deliver- 
ing the gas under slight pressure. Essentially the same 
process of purification is used with water gas. In recent 
years the horizontal retort for the distillation of the coal 
has been generally superseded by the inclined or vertical 
type. The charge of coal is admitted at the top, and the 
retort filled. When the distilling process is complete, the 
bottom of the retort is opened, and the residue, coke, 
falls out by gravity. 

The changes which take place when soft coal is thus 
burned out of contact with air are extremely compli- 
cated. The products formed are gaseous, liquid, and 



82 



HOUSEHOIvD CHEMISTRY 



solid. The liquid constituents which condense as coal 
tar yield on further treatment a number of substances 
such as benzol and anthracene, which are the basis of 
thousands of important organic compounds. The gas- 
eous products, which are combined as illuminating gas, 
are conveniently classified as follows : 

Impurities or diluents — oxygen, carbon dioxide, nitro- 
gen. 

Illuminants — ethylene, acetylene. 

Gas proper — hydrogen, marsh gas or methane, car- 
bon monoxide. 

Hydrogen sulphide is the only impurity in gas of any 
importance ; by its combustion sulphur dioxide and water 
are produced, finally resulting in sulphurous acid, which 
readily attacks fabrics and metals and bleaches many 
colors. Any hydrogen sulphide escaping combustion 
blackens lead acetate paper held far enough above the 
flame to be uninfluenced by the heat. 

Analyses of gas are given below : 





Water gas per cent. 


Coal gas 


Onrlinri flimcirip 


o.o 

12.6 

0.9 

27.3 

27.7 

27.7 

3.8 




Illuminants 


6.5 
0.9 

6.8 
41.1 
41.0 

3-7 


KJ2i,y^CU \ 

Carbon monoxide 

Hydrogen 

Marsh gas 




Ofltlfll A-Tirk^ATPT ..... ...... 


lOO.O 

25-4 


loo.o 

21.32 





HOUSEHOI^D CHE:MISTRY 83 

In a water gas, the candle-power is usually double the 
illuminants. 

The value of gas is expressed as candle-power, the 
unit being a standard sperm candle burning 2 grains 
per minute; hence a 25-candle-power gas would give 
as much light as 25 of the candles burning simultane- 
ously. The calorific value of the gas should also be de- 
termined as a measure of its quality for general pur- 
poses. 

The standard illuminating burner consumes 5 cubic 
feet per hour under a pressure of ij^ inches of water. 
This is used as a unit in all gas calculations. 

Two styles of meters are used — ^the wet and the dry; 
in the former the gas passes through a revolving drum 
partially submerged in water. The revolutions are regis- 
tered on dials by appropriate clockwork. Since this 
form of meter is liable to freeze and must always contain 
water, some of which is lost by evaporation, it has been 
largely superseded by the dry meter, which contains 2 
bellows alternately full and empty. A clockwork de- 
vice, similar to that used in the wet meter, keeps record 
on appropriate dials. Gas meters are subject to public 
test and are allowed an error of 2 per cent, either fast 
or slow. 

Chemical Changes During Combustion. — The common 
burner can only use gas of the following composition: 
methane, CH^, ethylene, C2H4, acetylene, CgHg, hydro- 
gen, H2, and carbon monoxide, CO. Combustion pro- 
ceeds according to the following equations : 



84 HOUSEHOLD CHEMISTRY 

CH, -f 2O, — * CO3 + 2H3O -- heat, no light. 

2H3 + O, «— 2H3O — heat, no light. 

2CO + Oj — 2CO3 ~ heat, no light. 

CjH, + O, »-> 2H2O + C, — less heat, some lighf. 

2C3H2 -\- Oj«»-^ 2H2O + 2Cj — less heat, more light. 

The Bunsen burner mixes the gas with O^ before 
combustion; this affects only the ethylene and acetylene 
as follows: 

C,H, + 3O, — ^ 2H,0 + 2CO3 — heat, no light. 
2C2H2 + 5O, — 2H3O + 4CO3 — heat, no light. 
Acetylene gas, C^Hq, is made by the action of water on 
calcium carbide as follows: 

CaC, + 2H,0 -* C,H, + Ca(OH), 
Calcium carbide is prepared by heating a mixture of 
lime and charcoal in the electric furnace. 
, Either the water is sprayed on the carbide, or finely 
pulverized carbide is sprinkled in water. 

Acetylene is only used in places where ordinary gas 
cannot be obtained, and is generally used at once. It 
may, however, be stored in an ingenious manner; strong 
copper cylinders are partly filled with acetone, and acety- 
lene pumped in until a certain pressure is obtained. By 
attaching one of these tanks to a lamp, a strong light 
may be maintained for many hours. The rationale of 
the process is that acetone dissolves acetylene under 
pressure and slowly gives it up when the tension is re- 
leased. 

Naphtha or Gasoline Gas. — Many isolated country 
houses depend for heat and light on this mixture. Out- 



HOUSEHOI.D CHEMISTRY 85 

side of the building and underground, is placed an iron 
tank for holding the hydrocarbon ; pipes lead to and from 
the house. In the house cellar is placed a large revolving 
drum driven by weights, for forcing air through the 
gasoline and driving back to the house the vapor-laden 
air. The process is satisfactory on a small scale but 
rather expensive, depending wholly on the price of the 
hydrocarbon. 

Blau gas is the invention of a German chemist, Her- 
man Blau. It is a mixture of hydrocarbons which are 
gases under ordinary conditions, but which liquefy under 
high pressures and low temperatures and are reconverted 
into gases when the pressure is released. In the making 
of Blau gas ordinary gas oil is distilled in retorts, the 
mixture of gases produced is purified, cooled and com- 
pressed up to 100 atmospheres. Hydrocarbons which 
liquefy under these conditions will absorb others which 
do not, and also so-called permanent gases such as 
methane and hydrogen. The liquefied gas is delivered 
for use in steel cylinders under high pressure, with a 
device attached for reducing the pressure before the gas 
enters the service pipes. One cubic foot of the liquefied 
substance expands to 400 cubic feet of gas. 

Pintsch Gas.— A similar method of compressing gas 
was inverted by Pintsch. Under his system the oil is 
distilled at about 1,000°, in order to produce a large 
amount of fixed gases. About 80 cubic feet of gas is 
obtained from i gallon of oil. These gases are stored 
in receivers under a pressure ordinarily of 6 atmos- 



86 HOUSEHOLD CHEMISTRY 

pheres. Pintsch gas is widely used for lighting railway 
cars, the receivers being carried underneath the car. 

EXPERIMENTS. \ 

Preparation of Methane — In a hard glass 8-inch test tube place 
a mixture of 6 grams of fused sodium acetate and 4 grams of 
soda lime. Close with a cork bearing a glass exit tube. Heat 
strongly and light the methane gas at the mouth of the tube. 
Complete the equation: 

CHgCOONa + NaOH «— 

Preparation of Ethylene — To 10 cc. of H2O in a beaker slowly 
add 30 cc. of concentrated HzSO* and cool. Put this mixture 
in an Erlenmeyer flask, fitted with a separatory funnel contain- 
ing 14 cc. of C2H5OH, and a delivery tube. Add clean sand to 
the flask to prevent bumping. Carry the delivery tube through 
the cork of a clean, dry, 12 or i6-ounce bottle. Pass another 
delivery tube out of the bottle and carry to a pan for collecting 
gas over water. Slowly drop the alcohol into the flask, heat 
gently, and collect i wide-mouth bottle and 2 narrow-necked 
bottles of the resulting gas. Test the gas in the wide-mouth 
bottle for inflammability. Write the reactions for the prepara- 
tion of the gas and its combustion. 

Into one of the narrow-necked bottles place i cc. of bromine 
water, close the bottle and shake. Explain, note odor, and write 
reaction. Into the second bottle put a very dilute solution of 
K2MN2O8 and add i cc. of 10 per cent. NaaCOa. Close and shake. 
Note the change. Look up von Baeyer's reaction for the double 
bond. 

Preparation of Acetylene — i. Drop a very small lump of cal- 
cium carbide into a test tube half full of water. Light the gas 
evolved and note its illuminating quality. 

2. Put 10 grams of calcium carbide in an Erlenmeyer flask 
provided with a separatory funnel and a delivery tube. Add 
water drop by drop through the funnel and collect the gas 
evolved over water, in small bottles or cylinders. Observe its 



HOUSEHOLD CHEMISTRY 87 

inflammability (Caution: acetylene mixed with air is explosive), 
its odor, and solubility in water and alcohol. Test with bromine 
water and K2Mn20s as under ethylene. Write reactions. 

3. Collect some illuminating gas in bottles containing bromine 
water and KaMuaOs respectively, as under ethylene, and shake. 
Note results. What does this show with regard to certain con- 
stituents of the gas? 



CHAPTER VII. 



CARBOHYDRATES. 

Carbohydrates are valuable organic compounds repre- 
senting one of the food principles. They originate in the 
development of vegetable life, being built up in the cells 
of all chlorophyll-bearing plants. These compounds 
contain the elements carbon, hydrogen and oxygen, and 
with some exceptions are aldehyde or ketone alcohols. 
The term carbohydrate, signifying carbon, with hydro- 
gen and oxygen in the proportion to form water, has 
lost its significance, for although important members of 
the group conform to this arrangement, e. g., sucrose 
(C12H22O11), glucose (CeHiaOg) and starch ^(CeHioOs), 
carbohydrate bodies are known which do not. Further- 
more, acetic and lactic acids which are not carbohydrates 
have respective formulas of C2H4O2 and CgHgOg. A 
better general term is saccharids or saccharoses. The 
usual classification subdivides the saccharids as follows: 

Monosacoharids. — Sugars which do not hydrolyze to 
simpler saccharids. They are alcohols joined with an 
aldehyde or a ketone group, and in consequence are 
called either aldoses or ketoses. The number of carbon 
atoms in the molecule is indicated by the terms tetrose, 
pentose, hexose, etc., and the full description may be, for 
example, aldohexose, or ketohexose. The hexoses are 
the most important members of this group. 

Disaccliarids. — The disaccharids yield two monosac- 
charid molecules of the hexose type on hydrolysis. 



HOUSEHOI.D CHEMISTRY 89 

Trisaccharids. — Raffinose, the most important example, 
hydrolyzes to three hexoses. 

Polysaccharids. — These bodies have large complex 
molecules which hydrolyze to an unknown number of 
monosaccharid molecules. 

The important carbohydrates are classified in detail 
below : 

Classification and Occurrence. — 

MONOSACCHARIDS. 

Pentoses, CgHjoOg. Arabinose, Xylose, etc. 

These do not occur free in nature, but result 
from the hydrolysis of polysaccharids called 
pentosans. (See page 91.) 

Hexoses, CeHigOg. 

Glucose or dextrose. Sometimes called grape 
sugar. Occurs in large amounts in grapes, is 
widely distributed in other fruits and plants, 
and is a product of the hydrolysis of most of 
the di-, tri-, and polysaccharids. Normal blood 
contains a small quantity, which is greatly in- 
creased in diabetes. 

Fructose or levulose. Sometimes called fruit 
sugar. Associated with glucose in nature, is a 
large constituent of honey, and is also a product 
of hydrolysis of some carbohydrates. 

Galactose. Has no common name and is not 
found free in nature. It is obtained by the hy- 
drolysis of lactose, raffinose, and the galactans. 



90 HOUSEHOLD CHEMISTRY 

DiSACCHARIDS. 

The important disaccharids have the formula 
C12H22O11. They are: 

Sucrose. Known as cane, beet or maple 
sugar, and found with glucose and fructose in 
the juice of many other plants. 

Maltose. The malt sugar of germinating 
grains. Also a product commercially of the 
partial hydrolysis of starch. 

Lactose. Known as milk sugar and found in 
the milk of most mammals. 

Trisaccharid. 

Raffinose, CigHggOie. Found in the germ of wheat 
and barley, in cotton seed, and usually in the sugar 
beet. It is commonly extracted from beet molasses. 

PpLYSACCHARIDS. 

The general expression wCgHioOg, n signifying that 
the molecule is an indefinite multiple of the for- 
mula given, is assigned to the hexosans of this 
complex group. Principal members are: 

Starch. The most important and widely dis- 
tributed polysaccharid. It occurs in plants gen- 
erally, especially in roots, tubers and seeds. 

Dextrin. Formed from starch by the action 
of heat alone, or by partial hydrolysis with 
enzymes or acids. Found in germinating cereals 
as a transition product. 



HOUSEHOI^D CHEMISTRY 9I 

Glycogen. Sometimes called animal starch. 
It is seldom found in plants, except in certain 
fungi and in varying amounts in yeast. It 
occurs in large quantities in the liver of animals 
and in the muscle of the scallop, and in smaller 
proportion in the blood and muscles generally. 

Cellulose. Constitutes the framework of the 
cell walls of all plant tissues. The cotton fiber 
is nearly pure cellulose. 

Inulin. A starch-like body extracted prin- 
cipally from dahlia tubers, but found also in the- 
artichoke and the roots of chicory. 

Galactans. Occur in the seeds of legumes; 
yield galactose on hydrolysis. 

Pentosans. {CJIfiJ». Araban and xylan, 
yielding arabinose and xylose on hydrolysis. 
Widely distributed in nature, especially in such 
substances as bran, wood, straw, etc. No con- 
siderable amount in food material. 

Natural Gums. Bodies which are generally 
classed with the polysaccharids, but the com- 
position of many of which is not definitely 
known. Pectin bodies belong to this group. 

Photosynthesis. — In the presence of sunlight the chloro- 
phyll-bearing plant cell takes carbon dioxide from the 
air, combines it with water, and polymerizes the product 
into a carbohydrate body. This photosynthesis may be 
represented by : 

6C0, + 6H,0 -^ C,H,,0, + 60,. 
7 



92 



HOUSEHOLD CHEMISTRY 



Such an expression does not take into account the inter- 
mediate products of the synthesis, about which more has 
to be learned. Baeyer, Erlenmeyer and others theorize 
that the carbon dioxide and water undergo double decom- 
position, and formaldehyde is formed and synthesized to 
a monosaccharid, according to the reactions : 

CO, + H,0 "--HCHO + 0,, 

6HCH0 «— C,U,fi,. 
The theory is supported by the fact that formaldehyde 
has been found in plant cells, and that it can be po- 
lymerized to fructose. According to Asher and Priestly, 
hydrogen peroxide is also produced in the above change, 
but is quickly decomposed to water and oxygen by a cata- 
lase in the leaf. 

Hydrolysis. — By enzyme action in the plant or animal 
body, or by the action of dilute acids and heat, di- and 
polysaccharids are hydrolyzed. The hydrolysis of a few 
of the important saccharids is given: 



Sucrose 


Knzymes. 
sucrase or invertase 


Products. 
Equal parts of 
■ glucose and fructose 
( (invert sugar). 


Maltose 


maltase 




/ Two molecules of 
\ glucose. 


Lactose 


lactase 




Equal parts of 
- glucose and galac- 
( tose. 


Starch 
Glycogen 


amylases 
(ptyalin 
etc.) 


diastase 


f Dextrins and 
< maltose. 



Raffinose is hydrolyzed by strong mineral acids to a 
molecule each of glucose, fructose, and galactose. Inulin 



HOUSEHOLD CHI:MISTRY 93 

is easily changed by acid hydrolysis to fructose ; it is not 
ordinarily attacked by enzymes. Cellulose and starch are 
considered anhydrides of glucose, and both yield glucose 
on acid hydrolysis. Ordinary cellulose is not, however, 
hydrolyzed by amylases or other enzymes, but by bac- 
terial action. 

The hydrolysis of pectic bodies is complex, and the 
cleavage products not definitely known. A substance is 
found associated with cellulose in the cell walls of unripe 
fruits to which the name pectose is given. As the fruit 
ripens, pectose is converted by enzyme action into pectin. 
This change can be brought about by boiling pectose with 
dilute acids or caustic alkalies, and the products include 
not only pectin in several forms but a number of acids. 
Pectin has the power of swelling in water and gelatiniz- 
ing, a property of which advantage is taken in jelly 
making. (See Chap. VIII.) 

In household practice many examples of hydrolysis 
occur, e. g., when starch and sugar are cooked with fruit 
acids ; in the process of caramelizing sugar or in making 
fondant. Sugar hydrolyzes much more quickly than 
starch. 

Optical Activity. — Nearly all carbohydrates are optic- 
ally active. Pure sucrose has a right rotation of 66° ; 
its hydrolytic products, glucose and fructose, show muta- 
rotation, but the average figure for dextro-glucose is 
-{-52.5°, that for fructose or levulose is — 93-8°. Since 
the pull of fructose to the left is greater by 41.3° than 
that of glucose to the right, it can be seen that an equal 



94 house:hold chemistry 

mixture of the two would have a left rotation, opposite 
to that of sucrose. For this reason the name invert 
sugar is given to the hydrolytic products of sucrose. A 
practical application of optical activity is made in the use 
of the saccharimeter (q. v.), by means of which the 
purity of sugar solutions is determined by estimating the 
amount of sucrose present. 

Solubility .^ — The mono- and disaccharids are soluble in 
water. Of the poly sacchar ids, starch is not soluble in 
cold water, but in hot water the granules burst and the 
contents become a gelatinous mass known as starch 
paste. Dextrin is soluble in cold water, more readily in 
hot; glycogen dissolves with an opalescent appearance; 
cellulose is not soluble in either hot or cold water. In 
strong alcohol the monosaccharids are sparingly soluble; 
of the disaccharids maltose dissolves most readily, sucrose 
t-o a limited extent, lactose is almost insoluble. All the 
polysaccharids are insoluble. 

Greneral Reactions. — Molisch's Test. — All soluble car- 
bohydrates respond to Molisch's reagent. To about 3 cc. 
of a dilute solution of any carbohydrate add 2 or 3 drops 
of Molisch's reagent, mix thoroughly, and carefully pour 
concentrated H^aSO^ down the inclined side of the test 
tube. A violet ring appears at the contact surface of the 
liquids. 

Furfural. — All carbohydrates yield some furfural on 
treatment with boiling HCl; the pentoses are distin- 
guished by the formation of large amounts. 

TTltimate Composition of a Typical Carbohydrate. — Place half 
a teaspoonful of dry granulated sugar in a clean, dry 6-inch test 



HOUS^HOI^D CHEMISTRY 



95 



tube. Heat gently in a Bunsen burner, observe the browning of 
the contents and the collection of moisture in the upper part of 
the tube. Explain. Increase the heat until dense fumes arise 
and then bring a flame to the mouth of the tube. What happens ? 
What are the fumes? Continue the heating until no more vola- 
tile products are given off, then cool the tube and remove some 
of the residue. What is it? Does it leave any residue on igni- 
tion? From the results of this experiment, what conclusions 
can be drawn as to the composition of sugar ? 

Glucose. 
Preparation. — Glucose is prepared commercially in the 
United States by hydrolyzing starch with very dilute hy- 
drochloric acid under pressure, neutralizing with soda 
ash, and evaporating the product in vacuo. It is sold 
in syrup and in crystal form. Commercial glucose con- 
tains varying amounts of dextrin. By carrying the hy- 
drolytic action further, pure glucose or grape sugar may 
be produced. 

Constitutional Structure. — That glucose is an aldo- 
hexose is proved by its reactions. The structural for- 
mula usually assigned to it is CH^OH (CHOH)^ CHO. 
The space configuration shown below illustrates the 
isomeric differences between glucose and the other im- 
portant hexoses: 



CH,OH 



CH,OH 



CH,OH 



OH— 

OH— 

H— 

OH— 



— H 
— H 
—OH 
— H 



OH— 

OH— 

H— 

H— 



— H 
— H 
—OH 
—OH 



OH— 

OH- 

H— 



— H 
— H 
—OH 
CO 



CHO 
glucose 



CHO 
galactoes 



CH,OH 

fructose 



96 HOUSEHOLD CHEMISTRY 

The most commonly occurring form of glucose rotates 
the plane of polarization to the right 52.5°. 

Properties. — Glucose is crystalline, soluble and diffu- 
sible. It crystallizes with difficulty from water, more 
readily from alcohol. In the first case the crystals ap- 
pear as thin plates in amorphous masses, usually contain- 
ing water of crystallization. Anhydrous needle or prism 
crystals may be obtained from alcohol. 

Nearly all yeasts readily ferment glucose, producing 
for the most part alcohol and carbon dioxide: CgHisOe 
— 2CO2 + 2C,H50H. 

Reducing Power. — Glucose shows its aldehyde charac- 
ter in its power of reducing metallic solutions such as 
are found in Fehling's, Barfoed's or Nylander's reagents, 
or alkaline silver nitrate. In the last a silver mirror 
is formed ; in Fehling's and Barfoed's the reduction from 
a higher to a lower copper oxide is shown by a color 
change from blue to red. Fehling's solution is the one 
most commonly used to determine the presence of a re- 
ducing sugar. The reactions taking place in changing 
from the cupric hydroxide to the cuprous oxide may be 
briefly indicated as follows: 

2Cu(OH)3 — 2CuOH + H,0 -}- O. 

Blue Yellow 

2CuOH — Cu,0 + H,0. 
Red 

The reduction of Fehling's by glucose may be made 
quantitative, 50 milligrams of glucose reducing 10 cc. 
of the standard solution. 



HOUSKHOIvD CHEMISTRY 97 

Formation of Osazone. — With phenylhydrazine glucose 
forms yellow needle crystals of phenylglucosazone, 
which are an identification test for this sugar. The 
change involves several reactions, in the first of which 
a hydrazone is formed : 

CH,OH(CHOH),CHO + NH^NHC^Hs — ^ 
Glucose Phenylhydrazine 

CH,0H(CH0H),CH:N.NHCeH5 + H,0. 

A second reaction takes place, more phenylhydrazine 
acting as an oxidizing agent on the adjacent = CHOH 
group : 

= CHOH + NH^NHCgHs — 

= CO + NH, + NH,C,H,. 
The CO left forms a second hydrazone group with phen- 
ylhydrazine present, the product being called an osazone, 
in this case phenylglucosazone : 

CH20H(CHOH)3COCHNNHCeH5 + NH^NHCgH^-v 
CH20H(CHOH)3C:N.NHCeH5CH:N.NHCeH5. 

Action of Acids and Alkalies. — When boiled with strong 
HCl, glucose is oxidized to levulinic acid, CH3COCH2 
CH^COOH ; with nitric, to saccharic acid COOH 
(CHOH)4COOH. If heated with strong caustic soda 
or potash a series of complex reactions of an oxidative 
nature take place, and a brown color results. All car- 
bohydrates with a free carbonyl group give this reaction. 

EXPERIMENTS ON GLTJCOSE. 

I. Taste, and note the sweetness. (Glucose is about three- 
fifths as sweet as cane sugar.) Roughly determine its solubility 
in hot and cold water and in alcohol. Does it react with iodine? 



98 hou^e:hoi.d chemistry 

2. Effect of Heat— Heat some dry glucose in a clean dry test 
tube; note the result. 

3. Effect of Strong Acid — To some dry glucose in a porcelain 
dish add cold concentrated sulphuric acid ; note the result. After 
allowing the test to stand for 5 minutes, heat gently and again 
note the result. 

4. Effect of Strong Alkali — To some glucose solution add 
strong caustic soda or potash and heat; note the result. 

5. Crystallization. — Make a syrupy solution of glucose and 
allow it to stand for several days. Do any crystals form? 

6. Fermentation. — Combine equal portions of compressed yeast 
with solutions of glucose, lactose, maltose and sucrose of equal 
strength, and starch paste. Fill the long arm of five bulb fer- 
mentation tubes with the five mixtures and close the bulb with a 
cotton plug. Stand in a warm place until fermentation begins. 
In each case note the rapidity with which carbon dioxide rises 
in the long arm of the tube and presses the liquid into the bulb, 
and draw conclusions as to the comparative action of yeast on 
the four sugars and the starch. Examine the liquid in the bulb 
for alcohol by (i) taste, and (2) heating with a small amount 
of iodine and sodium carbonate solution. 

7. Fehling's Solution Test — Into a 100 cc. flask put 5 cc. of 
copper sulphate solution and 5 cc. of alkaline Rochelle salt, mix 
and add 20 cc. of distilled water, cover with a watch crystal and 
boil for 2 minutes. No change should take place. Add a few 
cc. of a I per cent, glucose solution, boil vigorously for 2 min- 
utes, cool and note the result. Continue adding glucose and 
boiling until on cooling the blue color of the solution has faded. 
(50 milligrams of glucose are required.) 

Note. — If acid, the solution under test must be neutralized, as 
acids destroy the necessary alkaline condition of Fehling's and 
act in some degree as reducing agents. 

8. Barfoed's Solution — Add a few drops of glucose solution 
to a small amount of Barfoed's in a test tube; place the tube in 
boiling water for a few minutes. A clear red precipitate appear- 



HOUS^HOI^D CHEMISTRY 99 

ing around the edges of the Hquid indicates reduction to cuprous 
oxide. Barfoed's is an acid preparation— the test solution added 
to it must be neutral. 

9. Silver Mirror Test — To illustrate the reducing action of 
glucose on silver nitrate make a silver mirror as follows : Clean 
the article to be silvered — either a watch crystal or a small test 
tube — with nitric acid, water, and strong alcohol in the order 
mentioned, and place in contact with hot water. Make a strong 
solution of glucose. Take sufficient 5 per cent. AgNOs to fill 
the article, add ammonia cautiously until the precipitate formed 
almost disappears on shaking, then i or 2 cc. of the glucose 
solution. Mix quickly and fill the glass receptacle. When the 
reduction to metallic silver seems complete, pour off the solution. 

10. Preparation of Phenylglucosazone. — To 0.2 gram of pure 
glucose dissolved in 4 cc. of water, add 0.4 gram of phenyl- 
hydrazine hydrochloride, and 0.6 gram of crystallized sodium 
acetate. Filter the solution if not clear, close the test tube with 
a cotton plug, warm in a water bath until yellow crystals of 
phenylglucosazone appear. Observe these under a microscope. 

Grlucosides. — These are complex substances found in 
the vegetable kingdom, which on hydrolysis yield a car- 
bohydrate — generally glucose — and one or more other 
compounds. Many glucosides are known, together with 
the hydrolyzing enzymes which usually accompany them 
in the plant. A well-known example is amygdalin, found 
in bitter almonds, and the kernels of peaches, cherries, 
plums, etc. It is hydrolyzed by the emulsin of almonds 
to glucose, benzaldehyde, and hydrocyanic acid. An- 
other example is phloridzin, found in the root bark of 
apple, pear, plum and cherry trees, yielding glucose and 
phloretin by acid hydrolysis. 



lOO HOUSEHOI.D CHDMISTRY 

Fructose. 

The occurrence of fructose or levulose in nature has 
been given, also its space configuration (pp. 89 and 96.) 
The form of fructose found in nature rotates the plane 
of polarization to the left 93.8°. 

Fructose is harder to crystallize than glucose, but 
forms fine rhombic needles. It is somewhat sweeter than 
cane sugar. 

Reactions. — i. Resorcin gives a characteristic color 

reaction with fructose, due to the ketohexose nature of 

the latter. Carbohydrates such as cane sugar which 

yield fructose on hydrolysis, also give this reaction. 

Mix equal volumes of hydrochloric acid and fructose solution 
and add a few drops of resorcin solution. Warm; notice a deep 
red color and the formation of a brownish precipitate. 

2. Substances which, like fructose, have a ketone rad- 
icle linked to a = CHOH group, act as reducing agents 
in alkaline solutions such as Fehling's. 

3. Milk of lime precipitates fructose as an insoluble 
calcium compound, and thus can be used to separate the 
constituents of invert sugar, since the glucose compound 
remains in solution. 

EXPERIMENT. 

Dissolve 50 grams of pure honey in 250 cc. of water, cool 
with ice, and add 30 grams of slaked lime in small quantities, 
stirring constantly. Filter off the precipitate, wash it with a 
little water, press strongly to remove excess liquid, suspend it in 
water, and pass a stream of carbon dioxide through the mixture. 
The lime compound of fructose is decomposed. What precipi- 
tates? Filter, and evaporate the fructose in the filtrate to a 
syrup. Test with Fehling's and resorcin. 



HOUSEHOLD CHEMISTRY lOI 

If invert sugar is used for the above experiment decrease the 
amount to lo grams. 

4. With phenylhydrazine fructose gives an osazone 
identical with phenylglucosazone. 

Fructose may be obtained by extracting inulin from 
dahlia tubers and hydrolyzing. 

EXPERIMENT. 

Wash and grate several dahlia tubers; suspend the gratings in 
water. After standing, skim off and reject the floating mass. 
Mix the sediment of inulin with fresh water and when settled 
siphon off the liquid. The operation of washing should be 
repeated. Finally add more water and heat on a water bath for 
an hour, with a few drops of H2SO4 as the hydrolyzing agent. 
Neutralize with barium hydroxide, filter, and evaporate the 
filtrate at low heat to a syrup. Apply tests given above for 
fructose. 

Galactose. 

Galactose is an aldose, which is not found in the free 
state, but can be prepared by hydrolyzing lactose and 
separating the products, glucose and galactose, by crys- 
tallization of the latter from aqueous alcohol. It crys- 
tallizes in prisms which melt at 168°. Galactose is 
mutarotatory, with an equilibrium value of -[-81°. With 
phenylhydrazine it forms a compound similar to glucose. 
Galactose is fermentable, but not by ordinary yeast. 

Sucrose. 

Sucrose is an alcohol, with no free aldehyde or ketone 
group, as is shown by its formula: 



102 



HOUSEHOLD CHEMISTRY 



CH,OH 
CHOH 



CH,OH 

I 
, CH 



— CH 



O 



O 



CHOH 



CHOH 



CHOH 
CHOH 



' C 

/I 



-CH- 



-0 



/ 



CH,OH 



It therefore does not act as a reducing agent when pure. 
Chemically, it is identical whether produced from cane, 
beets, or maple sap. It crystallizes easily in large octo- 
hedrons, and is the most readily soluble in water of all 
the carbohydrates. In strong alcohol it is scarcely solu- 
ble. Sucrose hydrolyzes readily with sucrose and dilute 
acids; even heat alone is effective. In the last case the 
product is called caramel, and the beginning of the inver- 
sion corresponds with the first yellowing of the sugar. 



C12H22O11 -f H2O 



Glucose Fructose 

CfiH.jOfi + CfiH,,0« 



■12^6' 



Saccharimeter Test. — The purity of cane sugar, i. e., its 
freedom from invert, is determined with a modification 
of the polariscope called a saccharimeter. In one type of 
the instrument, using the Ventzke scale, the light passes 
through the polarizer, to the tube containing the sugar 
solution, and then through the analyzer. Behind this is a 
pair of quartz wedges arranged to neutralize the rotating 
effect of the sugar, and at the same time record the per- 
centage of rotation on a scale. The rotating effect of 



HOUS^HOI^D CHEMISTRY IO3 

pure sugar, + 66°, is read as loo per cent, on the scale. 
Any lesser figure indicates the percentage of sucrose 
present. 

For the saccharimeter test (using the Ventzke scale) 
26 grams of cane sugar are dissolved in the least quantity 
of water and made up to 100 cc. The solution must be 
clear and colorless. In case it is not, the cloudiness may 
be removed by means of a solution of basic acetate of 
lead, which precipitates dextrin and gummy matter. The 
operation is conducted as follows : 26 grams of the 
sugar are dissolved in 60-80 cc. of distilled water, a few 
cc. (not more than five) of the lead solution are added 
drop by drop as long as a precipitate appears, then double 
the quantity of alumina cream and enough distilled water 
to reach the 100 cc. mark. The mixture is shaken vigor- 
ously and allowed to stand for a few minutes for the 
bulky precipitate to settle. It is then filtered through dry 
paper, the first 20 cc. of the filtrate being rejected. The 
tube of the instrument is filled with the solution, the 
rotating effect determined, and the percentage of purity 
read on the scale. 

EXPERIMENTS ON SUCROSE. 

1. Roughly determine its solubility in cold and hot water, and 
in alcohol. Is the solubility affected by heat? 

2. Crystallization — Make a hot syrupy solution of sugar and 
suspend in it a piece of glass rod by a thread. Set aside and 
allow to cool and after a time carefully examine the crystals of 
cane sugar. 

3. Effect of Dry Heat — Boil down sugar solution to dryness 
and note the result. 

4. Effect of Strong Acid. — Drop some concentrated sulphuric 



104 HOUSKHOI.D CHEMISTRY 

acid on dry sugar, note the result and compare with starch and 
glucose. 

5. Add a weak sugar solution to boiling Fehling's reagent. If 
pure there should be no reduction, 

6. Hydrolysis— «Inversion."_Boil a dilute sugar solution with 
a few drops of concentrated hydrochloric acid, cool, neutralize 
with sodium carbonate and add to Fehling's solution; note the 
result and compare with glucose. What change has taken place? 

7. Test hydrolyzed and unhydrolyzed sugar solution with 
Barfoed's. 

8. Effect of Strong Alkali — To 10 cc. of a weak sugar solution 
add some strong caustic soda, heat and note the result; compare 
with glucose. 

9. Specific Test — To 15 cc. of the clear Hquid, add 5 cc. of 
cobalt chloride (5 per cent.) and 2 cc. of caustic soda (50 per 
cent,). Sucrose gives an amethyst-violet, permanent on heating. 
Glucose gives a turquoise-blue, turning to green on standing 
some time, or on gentle heating. This test may be used on con- 
densed milk, honey, preserves, etc. 

' 10. Caramel Test. — Boil a strong solution of sugar until it has 
turned brown (caramel), cool, dilute and test some of the liquid 
with Fehling's solution. 

11. Saccharimeter Test — Determine the purity of samples of 
cane sugar by the saccharimeter. 

12. Formation of Sucrosate — Sucrose unites with metallic 
hydroxides such as calcium and barium to form sucrosates. Cal- 
cium sucrosate may be prepared by saturating milk of lime with 
sucrose at low heat. The product is commonly called viscogen, 
and is used as a thickener in whipping cream, etc. 

13. Resorcin Test — To a solution of cane sugar add an equal 
volume of HCl and a few crystals of resorcin. Warm. A deep 
red color appears, due to the formation of fructose. 

Maltose. 
Maltose occurs in nature as a product of the hydroly- 



HOUSEHOLD CHEMISTRY 



105 



sis of starch by the unorganized ferment diastase during 
germination, and by ptyalin in salivary digestion. It is 
an aldose, as is shown by its formula : 

CH,OH 1 CH, 



CHOH 



r 



— CH 



O 



CHOH 



CHOH 



J — CH- 



CHOH 

I 
O CHOH 

CHOH 

I 
CHOH 

I 
-I CHO 



On hydrolysis, by maltase or dilute acids, maltose yields 
two molecules of glucose: 

Glucose 
C,,H,,0,, + H,0 -> 2C,H,,0,. 

Maltose like lactose contains a free carbonyl group 
and hence reduces Fehling's solution directly — 80 milli- 
grams reduces 10 cc. of the reagent. 

Maltose is readily soluble in water and crystallizes 
from it in fine plates in the hydrated form CiaH^aOn, 
H2O. It becomes anhydrous by drying at 100°. In the 
hydrated state it dissolves more freely in alcohol than do 
sucrose and lactose, and in this way also can be separated 
from its mixture with most dextrins, which are precip- 
itated by alcohol of over 60 per cent, strength. Maltose 
crystallizes from alcohol in the anhydrous state. 

With phenylhydrazine, yellow crystals of phenylmalt- 



I06 HOUSEHOLD CHEMISTRY 

osazone form which resemble irregular daisy petals or 
knife blades. 

EXPERIMENTS ON MALTOSE. 

Preparation of Diastase in the Eorm of Malt. — Malt is pro- 
duced during the germination of barley and other cereals. Pre- 
pare it as follows: Spread out a thin layer of barley grains 
(one tablespoonful) on the cover of a small pasteboard box, 
moisten with warm water and keep in a moderately warm place. 
Each grain will soon begin to sprout. When the acrospire has 
grown the length of the grain, dry the mass in an oven at a low 
temperature and keep bottled. Make malt extract by grinding 
the grains coarsely and extracting them with loo cc. of warm 
water. Note the taste and odor of the liquid. Keep for future 
use. 

Preparation of Pure Maltose — Make a thin paste of starch 
and boiling water, cool to 65° and add 10 cc. of malt extract, 
prepared as above, and continue the heating at 65° for half an 
hour. From time to time test small portions of the Hquid with 
iodine solution. When the liquid fails to react blue, cool the 
balance of the solution, divide in 6 parts and test as follows: 

1. Solubility in Alcohol — ^Add some of the liquid to strong 
alcohol, allow to stand and note the white precipitate of dextrin ; 
the liquid contains maltose. 

2. Bffeci of Pehling's Solution. — To 10 cc. of Fehling's solution 
add a few drops of the liquid, boil for 2 minutes and note the 
reduction; add more of the solution and boil again; repeat until 
the reduction is complete. 

3. Test with Barfoed's reagent. 

4. Apply the fermentation test. 

5. Test with strong caustic soda or potash. 

6. Repeat the phenylhydrazine test. Compare with glucose. 

Note. — The above tests may be made on commercially pre- 
pared maltose. 



HOUSEHOIvD CHEMISTRY I07 

Lactose. 

Lactose, or milk sugar, is a disaccharid containing a 
free carbonyl group. The structural formula for maltose 
(q. V.) may be used to represent lactose also. It is a 
reducing agent, 67.8 milligrams being required to reduce 
completely 10 cc. of Fehling's. 

Lactose is less soluble in water than sucrose or maltose. 
Five or six parts of cold water are required for solution, 
or about two and one-half parts of boiling water. When 
crystallized from water at low temperature it contains 
one molecule of water of crystallization, which is lost by 
heating the crystals to 130°. Lactose is insoluble in 
alcohol. 

With phenylhydrazine yellow crystals of phenyl-lact- 
osazone are formed, which resemble chestnut burrs. 
Ordinary yeast does not ferment lactose, but lactic fer- 
ments convert it into lactic acid and alcohol. Lactose 
readily undergoes butyric acid fermentation. 

By hydrolysis with lactase or dilute acids lactose is 
converted into a molecule each of glucose and galactose. 

Glucose Galactose 

CjgHj^Oii -f H2O »-^ CgHijOg + CgHi^Og. 

EXPERIMENTS ON LACTOSE. 

Preparation — Allow milk to stand until well soured; filter. 
Faintly acidulate the whey with dilute acetic acid and heat to 
coagulate protein material. Filter, and evaporate the filtrate 
over hot water to crystallization. The crystals are crude lactose. 

Take some of the lactose so prepared, or the commercial form, 
and make the following tests : 

I. Note the hardness and slightly sweet taste, due to the 
limited solubility. 
8 



io8 house:hoi.d chemistry 

2. Try its solubility in water and in alcohol. 

3. Treat some dry powdered lactose with concentrated sul- 
phuric acid; note the result. 

4. Try the caustic soda reaction. "^ 

5. Apply the Fehling's test. 

6. Test with Barfoed's reagent. 

7. Make a weak solution of lactose in water, let it stand at 
least 24 hours in a moderately warm place, and then test for 
acidity. 

8. Make the phenylhydrazine test, compare with glucose and 
maltose. 

Starch. 

Starch is the most widely distributed carbohydrate. 
It is found in varying proportions in leaves, stems, 
woody tissues, roots, tubers, fruits and seeds, but is es- 
pecially abundant in the cereal grains and in tubers such 
as the potato. The formula ^(CeHioOs) is used to 
express its large and complex molecule, but soluble starch 
- — or its principal constituent, amylo-dextrin — is some- 
times represented as (Ci2H2oOio)54- 

Physical State. — Pure starch is a white, powdery sub- 
stance, colloidal and granular. The granules are definite 
m average size and appearance according to their source. 
Potato starch has one of the largest granules. They 
are ovoid in shape, and show concentric layers which in- 
crease in thickness with their distance from the nucleus 
or hilum. The size increases with age. As a general rule 
the large granules are more easily disrupted by heat. The 
outer layer of starch granules is known as starch cel- 
lulose ; the contents as granulose or amylose. 

Effect of Heat. — In hot water the outer layer of starch 
granules is ruptured and the contents gelatinize, form- 



HOUSEHOI^D CHEMISTRY lOQ 

ing a partial solution known as starch paste. The tem- 
perature of gelatinization varies from 65° to 85°, ac- 
cording to the kind of starch. Root and tuber starches 
gelatinize at a lower temperature, as a rule, than cereal 
starches. According to some investigators^ gelatinization 
is caused by a mucilaginous substance, amylo-pectin, 
found in the granule. This body does not give the iodine 
reaction, and swells without dissolving in hot water. 

Ordinary air-dried starch is dextrinized at temperatures 
from 160° to 210°. Reducing sugars may possibly be 
formed. With higher temperatures, and out of contact 
with air, starch yields products similar to those formed 
in the dry distillation of wood. 

Effect of Low Temperature. — On cooling, starch paste 
contracts. Its greatest contraction is at freezing point, 
when a permanent separation of water and starch takes 
place to a considerable extent, and the starch dries out 
as a powdery mass. This substance is often noticed on 
starched clothes dried after being frozen, and such 
clothes have lost most of their stiffness. 

Soluble Starch. — Starch is manufactured in several 
grades with regard to thickening quality. With long 
continued heating or heating under pressure at 130^-150°, 
with ten times its weight of water, a form of starch is 
prepared which goes into true solution. It does not 
gelatinize, but gives the iodine reaction and does not 
reduce Fehling's. 

Eeaction with Iodine. — This is the most characteristic 

test for starch. A deep blue color is produced whether 

^Maquenne and Roux: Ann. Chim. Phys., 1906 [8], 9, 179. 
Matthews and Lott: 7. Inst. Brewing, 191 1, 17, 219-266. 



no HOUSEHOLD CHEMISTRY 

the granule is ruptured or not. The compound formed 
is called starch iodide. 

Action of Acids and Alkalies. — On boiling with dilute 
(2 per cent.) HCl or HgSO^, starch is hydrolyzed to 
dextrins and maltose, and finally to glucose. Concen- 
trated H2SO4 causes a complete carbonization of air-dry 
starch in a short time. Strong HCl on dry starch causes 
a swelling of the granules and in a short time a change 
to the soluble form. If the action is continued for a 
few days, hydrolysis of the granules to achroodextrin, 
maltose and glucose results, while the starch cellulose 
remains unchanged. With nitric acid various products 
are formed according to conditions. On boiling with 
strong HNO3 (specific gravity 1.2) starch is converted 
into oxalic acid. With cold concentrated HNO3 com- 
pounds may be formed similar to the nitrates of cellulose. 
In presence of cold strong fixed alkali, starch is solu- 
ble with partial hydrolysis and usually the product has 
a distinct yellow color; weaker solutions have very little 
effect unless heated. 

Action of Enzymes. — Amylases, whether the diastase of 
grains, the ptyalin of the saliva, or the amylopsin of 
the pancreatic secretion, hydrolyze starch to maltose. 
The first reaction is a quick change of starch paste to 
soluble starch. Shortly after, the blue color with iodine 
gives place to a reddish brown, showing the presence 
of erythrodextrin. At the same time maltose is formed. 
The change may be expressed as : 

(C,H„0,). +HOH -- C„H,,0„ + (C,H,„0,).. 

maltose dextrin 



HOUSEHOI.D CHEMISTRY III 

As the action continues an achroo dextrin stage is reached 
where the iodine ceases to act, and the amount of re- 
ducing sugar is increased. According to Maquenne and 
Roux, the maltose is produced from the principal con- 
stituent of the granule, amylose, and the residual dextrin 
comes from the amylo-pectin, which is slowly changed 
by enzyme action, but does not yield a reducing sugar. 
Experiments by these investigators and others show 
about 80 per cent, of maltose formed after 2 hours of 
diastatic action. Hydrolysis with diastase proceeds most 
rapidly at a temperature of about 55°. 

Fermentation. — Various organisms are known which 
ferment starch to alcohol. With yeast there is no direct 
fermentation; if a diastatic enzyme is present in the 
starch, hydrolysis to maltose may take place, in which case 
the maltase in ordinary yeast carries the hydrolysis to 
glucose. This in turn is converted by zymase to various 
substances, chiefly carbon dioxide and alcohol. 

EXFEEIHENTS ON STARCH. 

1. Occurrence of Starch. — Examine a thin section of potato 
under the microscope. Make a careful drawing of the structure 
of the cells and the granules within. Cover the section with a 
thin glass and introduce a minute trace of iodine solution at the 
edge of the cover glass. Note and make a colored (blue pencil) 
diagram of the result. 

2. Extraction of Starch. — Clean and peel one end of a small 
potato, rub it on an ordinary grater, collect the gratings in a 
beaker of cold water, strain, allow the cloudy liquid to stand 
until starch settles. Pour off liquid and use the sediment for 
the following tests : 

3. Effect of Dry Heat — Gently heat half an inch of dry starch 
in a clean, dry test tube. Observe and explain condensed moist- 



112 HOUSEHOLD CHEMISTRY 

ure in the cooler part of the tube. Increase the heat somewhat 
and note the odor of the evolved vapor and the color of the 
starch: What does it suggest? Now heat strongly until pnly a 
black residue remains. What is it? 

4. Effect of Strong Acid — To a small portion of dry starch 
in a porcelain evaporating dish add a few drops of concentrated 
sulphuric acid ; note the result and after a short time heat gently 
and observe again. 

5. Solubility. — Treat a small portion of finely pulverized dry 
starch with cold water, filter a portion and examine the filtrate 
for dissolved material, by evaporating to dryness, also by the 
iodine test. 

6. Starch Paste — Boil the remainder of the starch and water 
mixture. Filter some of the gelatinized product and test a por- 
tion of the filtrate with iodine, and with alcohol. What per 
cent, of the latter is required for precipitation? 

7. Conditions for Iodine Tests — To another portion of the 
cooled filtrate add iodine solution, gently heat and allow to cool. 
Note the result. Now boil for some time and cool; the color 
will not return. Why? 

To some starch solution in a test tube add a small portion of 
caustic soda and a few drops of iodine solution and note the 
result. Repeat the experiment using dilute sulphuric acid instead 
of NaOH. 

Test the effect of glucose and tannic acid on iodide of starch. 

8. Effect of Tannic Acid — Add a solution of tannic acid to 
some starch solution. Note the result, also any change effected 
by heating. 

9. Starch a Colloidal Substance — Partly fill a diffusion thimble 
with thin starch paste, and stand it in a beaker of cold water. 
After some time, test the water for starch with iodine. Does 
this explain why starch is not lost through the cell walls of the 
plant ? 

Note. — For the following experiments use a i per cent, starch 
solution. 

10. Acid Hydrolysis — To 75 cc. of starch solution add 2 cc. of 



house:hoIvD chemistry 113 

strong hydrochloric acid and boil until clear, using a reflux con- 
denser. At this point, a small quantity of the cooled liquid should 
give no blue coloration with iodine. If this is not the case add 
10 drops more of the same acid and boil some minutes longer, 
or until a small portion gives no test with iodine. Neutralize 
the remainder of the liquid with sodium carbonate solution, add 
10 cc. to Fehling's solution and boil. If reduction does not take 
place add more of the solution and reboil. 

2. Mix about i gram of starch with 10 cc. of strong HCl and 
allow the mixture to stand for 15 minutes. Now pour off a 
small portion and add an excess of cold water. A milky pre- 
cipitate of soluble starch results. Filter this and test its solu- 
bility in hot water. Allow the remainder of the acid mixture to 
stand for several days, until the viscous mass becomes clear and 
separates into 2 layers. The upper layer contains starch cellu- 
lose. Remove and test with iodine. Neutralize the lower layer 
and make the Fehling's test. 

11. Enzyme Hydrolysis — i. Take about 25 cc. of clear dilute 
starch paste in a small beaker and add 2 or 3 cc. of undiluted 
saliva which has been filtered through coarse filter paper. 

Keep at body temperature and from time to time pour off 
small portions and test with iodine solution, keeping each for 
comparison. Note the gradual change from blue to red to yellow 
and finally to colorless. When this stage is reached, add a small 
portion of the material to Fehling's solution, boil, and note 
reduction due to maltose. 

2. To 25 cc. of dilute starch paste add about 5 cc. of diastase 
solution and keep at 55°. Test portions from time to time with 
iodine until the test fails to give a color (maltose). At this stage 
boil the remainder of the solution with about 25 drops of dilute 
sulphuric acid for 10 minutes. Neutralize and test this with 
Fehling's solution for glucose. 

12. Mix TO cc. of dilute starch solution with an equal volume 
of alcohol (95 per cent.), add to the mixture a saturated solu- 
tion of barium hydroxide as long as precipitation occurs. Filter 
and wash the precipitate sUghtly. Test the filtrate with iodine. 



114 HOUSKHOI.D CHEMISTRY 

Suspend the precipitate in water and pass a rapid current of 
carbon dioxide through the mixture for several minutes. Filter 
and test the liquid with iodine solution. Explain. 

Dextrin. 

The dextrins are colloidal compounds, soluble in water, 
and precipitated by strong alcohol. As starch hydrolysis 
proceeds a number of dextrins are formed: the dextrin 
which gives a red-brown color with iodine is termed 
erythrodextrin ; that which is forming as iodine ceases to 
act is achroodextrin. A maltodextrin is known to which 
the formula 6(C6Hio05)H20 has been assigned. It ap- 
pears to be a chemical combination of one part maltose 
and two parts dextrin, and is a reducing substance. Dex- 
trins proper are not considered to have reducing power 
when pure. 

Dextrins are used to a great extent in textile and 
other industries for sizings, as a medium for colors in 
textile printing, as gum, paste, etc. They also form about 
half the carbohydrate material in corn syrup. 

Preparation. — Dextrin or "British Gum" is prepared 
commercially by two methods: (i) Dry starch is heated 
to 200°-250° over an oil bath, in a steam jacket, or other 
device to insure the requisite temperature without char- 
ring. The product is dark in color, but has good adhesive 
quality. (2) The starch is moistened with nitric or hy- 
drochloric acid, dried, and heated to i40°-i7o°. The 
result of this partial hydrolysis is a light colored dextrin 
containing some sugar, and having, therefore, less ad- 
hesive power. Dextrin may be prepared more con- 
veniently by heating a strong starch paste with moder- 



HousEHOi^D che;mistry 1 15 

ately dilute sulphuric acid until clear, cooling and pre- 
cipitating by adding to ethyl alcohol. 

EXPERIMENTS ON DEXTRIN. 

Solubility. — Compare the solubility of dextrin in cold water 
and in boiling water. 

To successive portions of cooled dextrin solution in test tubes 
add: 

1. Alcohol up to 60 per cent, by volume. 

2. Iodine solution. 

3. Caustic soda and iodine solutions. 

4. Sulphuric acid and iodine solutions. 

5. A few drops of ammonia and basic acetate of lead; note 
the result. 

6. To boiling Fehling's solution; if pure there will be no 
reaction. 

7. Tannic acid as under starch. 

8. For the hydrolysis of dextrin by enzyme action, follow the 
method given under starch. 

Glycogen. 

Glycogen is known as animal starch, since it appears 
as the reserve carbohydrate in the developing cells of 
animal organisms. It is present in the liver in consider- 
able quantity ; to a less extent in blood, muscle and several 
glands. Its formula is (CeHioOs)^. In appearance 
glycogen is a white, amorphous powder. It is soluble 
with opalescence in water, insoluble in strong alcohol, and 
hydrolyzes as starch does with diastase or with acids. 
Glycogen gives a brownish red color with iodine, does not 
reduce Fehling's, and is not fermentable by yeast. It may 
be extracted in considerable quantity from the large 
muscle of the scallop, as follows : 



Il6 HOUSEHOLD CHEMISTRY 

Preparation. — Grind a mixture of scallops and sand in 
a mortar, transfer to a beaker, add enough water to 
cover the mass and boil. This dissolves the glycogen 
and partially precipitates the proteins, which are now 
completely precipitated by slightly cooling and adding 
a few drops of acetic acid. Filter and add the filtrate to 
alcohol (95 per cent.). Glycogen will come down as a 
white precipitate. Allow to settle, decant the clear liquid, 
and filter the residue. 

Apply the following tests to the glycogen thus ob- 
tained : 

1. Solubility in water; look for opalescence. 

2. Solubility in 10 per cent, sodium chloride solution. 

3. Solubility in hydrochloric acid. 

4. Solubility in caustic potash. 

5. Reaction with iodine solution. 

,6. Boil a dilute solution of glycogen in a beaker for 15 minutes 
with 2 cc. of dilute hydrochloric acid, neutralize with sodium 
carbonate and test with Fehling's solution. What change has 
taken place? 

Celluloses. 

These compounds, represented by the general formula 
wCeHioOg, are at once the most complicated and stable 
of the carbohydrates. 

They may be roughly divided into the simple and 
compound celluloses, the former unicellular in structure 
and the latter multicellular. 

Cotton, thistledown, and the internal fibrous network 
of grains and vegetables are simple celluloses and occur 
as ribbon-like bands with curled edges and a character- 
istic corkscrew twist. These forms contain little protein,. 



HOUSEHOLD CHEMISTRY II7 

gum, fat or mineral matter. Flax, grasses and woody 
fiber are compound celluloses, occurring for the most part 
as jointed rods or tubes, and are highly charged with pro- 
tein, fat, gum and mineral matter. Cotton is the only 
unicellular form of cellulose of industrial importance, 
while the multicellular type has many representatives, i, e., 
linen, hemp, jute, ramie and a great variety of woods. 

The treatment of cotton does not involve any exten- 
sive chemical operations, but is chiefly confined to 
mechanical manipulation. The compound celluloses on 
the other hand require complex and prolonged chemical 
or bacterial treatment before the fiber is ready for the 
operations of spinning, weaving and dyeing. Woody 
fiber is now generally used for the preparation of the 
felted fabric known as paper. It is necessary in this case 
to remove all impurities by chemical means, and to break 
up the long fibers by grinding before the fabric can be 
prepared. 

General Properties of the Celluloses. — Celluloses are 
insoluble in water hot or cold, and in weak acids or 
alkalies. Strong acids and alkalies cause them to hydro- 
lyze; in some cases soluble forms result by heating or 
prolonged action in the cold, or by a combination of both 
methods. Generally speaking, the action of acids is more 
rapid. When partially hydrolyzed they are colored blue 
in the presence of iodine. Nitric acid in concentrated 
form converts cellulose into nitrates of varying composi- 
tion, containing one to six nitric groups — the form de- 
pending on the duration of the nitrating process. All of 
these compounds are very unstable and dissociate into 



Il8 HOUSEHOLD CHEMISTRY 

water, carbon dioxide and nitrogen, when slightly heated ; 
hence their use as explosives. Cellulose nitrates, unlike 
cellulose, dissolve in ether, alcohol or acetone or mixtures 
of these solvents (collodion) and on evaporation yield 
transparent structureless films, used in medicine, photog- 
raphy and for the preparation of artificial silk. Am- 
moniacal cupric oxide (Schweitzer's Reagent) and con- 
centrated zinc chloride dissolve simple cellulose on gentle 
warming. Hydrocellulose precipitates from these solu- 
tions on acidifying with acetic acid. 

Lignocellulose (wood) yields oxalic acid on treatment 
with nitric acid, and oxalate of potash on fusion with 
caustic potash. 

Cellulose fibers are characterized by high capillary 
capacity and heat conductivity; hence their use for lamp 
wicks, toweling and summer clothing. These properties, 
however, may be much modified by tight twisting and 
close weaving, as in the case of canvas. 

While ordinary cellulose is considered an anhydride of 
glucose, and hydrolyzes to glucose, a hemi-cellulose is 
known which yields mannose, galactose, arabinose and 
xylose on hydrolysis, but no glucose. 

EXFEEIMENTS ON CELLTJLOSE. 

(a) Effect of Heat (Charring) — Heat a piece of fibrous 
material in a clean dry test tube. Note the odor of the gases 
evolved and test the vapor with blue litmus paper. Examine the 
charred mass with a magnifier. 

(b) Solubility in Water. — Try to dissolve some fibrous 
material in water. 

(c) Solubility in Zinc Chloride — Dissolve some absorbent 
cotton in acid zinc chloride solution (ZnCla dissolved in twice 



HOUSEHOI.D CHEMISTRY II9 

its weight of concentrated HCl). Precipitate by dilution and 
compare the result with the original substance. 

(d) Solubility in Schweitzer's Reagent — Dissolve some ab- 
sorbent cotton in Schweitzer's reagent, add the resulting solution 
to 95 per cent, alcohol and compare the precipitate with the 
original substance. 

(e) Structure — Examine carefully the structure of cotton and 
linen fibers under a microscope. 

(/) Crude Fiber — Crude cellulose of wood, grains, etc., is 
determined as follows : 

Take i gram of the dried ground sample, boil with 100 cc. 
oi 1% per cent, sulphuric acid, when cool strain through muslin. 
Wash once with hot water. Scrape the residue from the muslin 
and boil it with 100 cc. of i^ per cent, caustic soda. Strain 
again through the same piece of muslin, wash with hot water, 
then with alcohol, and finally with ether. Weigh the dried 
residue. 

Nitrating. — Treat a piece of filter paper or some absorbent 
cotton with a cooled mixture of 20 cc. concentrated HaSO* and 
ID cc. concentrated HNO3. Keep the solution cool. Several 
nitrates of cellulose may form. The hexa- and penta-nitrates are 
the most prominent. The hexa-nitrate of cellulose is called gun 
cotton. Wash the product in water and dry. Test its inflam- 
mability, and its solubility in a mixture of 40 per cent, alcohol 
and 60 per cent, ether. The clear solution is collodion. Observe 
how a film of it hardens in the air. When pressed through 
capillar^' tubes, filaments are produced, which are denitrated and 
further treated to form one class of artificial silk — the nitra- 
cellulose or pyroxylin. 

Mercerization. — Stretch some cheesecloth or muslin tightly over 
a porcelain dish and immerse for 15 minutes in a 25 per cent, 
solution of caustic soda, at a temperature of about 20". An 
alkali-cellulose forms, and the cloth appears semi-transparent. 
Wash free from alkali, dry, and notice the appearance of the 
mercerized cotton compared with the original material. Try 



120 HOUSEHOI.D CHEMISTRY 

its reaction with iodine. The cotton has become cellulose hy- 
drate, «(C«Hio05)H20. 

Methods of Distinguishing Cotton from Linen.— The 
microscope is the one reliable means of differentiating 
these fibers, since full-bleached linen and cotton are 
practically identical in chemical composition. How- 
ever, the following tests are helpful if a microscope is 
not available: 

Breaking and Burning Tests — Unraveled threads of linen 
fabrics are untwisted and broken by holding between the thumbs 
and index fingers and pulling apart slowly and steadily. Linen 
parts slowly, and with pointed ends; cotton breaks suddenly 
with tasselled ends. Burn a small tuft of each fiber and note 
the condition of the fiber ends. 

Sulphuric Acid Test. — Dip a piece of union toweling in con- 
centrated H2SO4, for about i>4 minutes. Remove, wash, and note 
the comparative strength of the cotton and linen threads. Cotton 
■will be destroyed in 2 minutes or less; linen as a rule not so 
quickly. 

TESTS ON LIGNOCELITILOSE. 

(a) Structure — Examine carefully the character of the fibers, 
e. g., hemp or jute. 

(h) Phloroglucinol Test — Phlorogludnol, in HCl, gives a deep 
magenta coloration with any of the lignocelluloses. 

The reagent is prepared by dissolving the phenol to saturation 
in HCl (1.06 specific gravity). 

(c) Saturate moist jute fiber, held in a glass tube, with 
chlorine gas and then pass SO2 through it. Note the character- 
istic reaction, a deep magenta color. 

TESTS ON PAPER. 

Determine starch as filler with iodine solution. Determine 
"size" by moistening the paper with Millon's reagent and warm- 
ing gently. 



HOUS]eHOI.D CHEMISTRY 121 

Parchment Paper — Dip starch-free paper in a cold mixture of 
water and H2SO4 (2 :3), withdraw quickly, wash in clear water 
and dry. Compare with an untreated sample. Make the iodine 
test. (Cellulose in the presence of certain dehydrating agents 
responds to iodine.) 

PRACTICAL WORK ON CARBOHYDRATES. 

I. Examination oS' Cereals. 

Materials — Ready-to-eat cereals of different types — flaked, 
and shredded. Uncooked cereals — rolled and granular. 

Method: i. Grind samples fine in mortar. Make cold water 
solution. Filter. Examine filtrate as follows: 
0. For soluble starch (iodine). 

b. For dextrin. Add carefully to 95 per cent, alcohol. 

Note precipitate. Continue adding the filtrate, observ- 
ing whether the precipitate decreases in amount. If 
so, the alcohol has been diluted below 60 per cent., 
and dextrin has gone into solution. Starch remains 
insoluble. If much dextrin is present iodine will show 
it. 

c. For reducing sugar. Make Fehling's and Barfoed's 

tests. 

d. For protein. Make biuret test (see p. 148). 

2. Stain a portion of the residue with iodine and examine 
under the microscope for unbroken starch granules. 

3. Ash determination. Char 5-10 grams of oats, bran or corn 
meal in a 3-inch porcelain dish, cool and extract the mass with 
boiling distilled water. Test this solution for K, Na, Ca, Mg, 
SO4, CI and PO4. Dry the extracted char and ash in a muffle, 
cool, add a few drops of concentrated HCl and take up with dis- 
tilled water. Filter if necessary and test the filtrate for Fe, Ca, 
Mg, PO4. 

II. Cooking oe Cereai^s. 
Cook different cereals for the minimum time stated on the 
package. Observe condition of granules under microscope. 



122 HOUSEHOLD CHEMISTRY 

(Note that a ruptured granule does not always lose its form or 
contents.) Observe again after a longer cooking. 

III. Prepared Soups. 
Treat prepared dried puree soups as in II and observe. 

IV. Crackers, Bread, Toast, etc. 
Examine as in I for unchanged and changed starch, dextrin 
and reducing sugar. Compare under microscope stained slides 
of bread from crust and center of loaf. 

V. Potatoes. 
Bake and boil until cooked. Examine under microscope. 
Make salivary digestion test on well-cooked potato, examining 
under the microscope the condition of the granules in the dextrin 
and maltose stages. 

VI. Hydrolytic Changes. 

Test sugars for reducing action after boiling with cream of 
tartar (fondant making), lemon juice, or other acid fruit juice. 
Note time required for hydrolysis and the completeness of the 
change. Make similar tests on starch and compare with sugar 
as to quickness of action. 

VII. Honey and Syrups. 
Test for cane and invert sugars. 

VIII. Thickening Power. 

Note comparative thickening power of potato, corn, and wheat 
starches, and time required for cooking. 



CHAPTER VIII. 



FRUITS AND FRUIT JUICES. 

Composition. — Analyses of fresh fruits show such simi- 
larities in composition that a general description is suf- 
ficient. The percentage of water is always high, being 
from 75 per cent, to more than 90 per cent, in the edible 
portion.^ The next highest constituent is the carbohy- 
drate bodies. 

The carbohydrates in ripe fruits are principally glu- 
cose and fructose. Starch and acids decrease as fruit 
ripens; invert increases. Sucrose normally disappears 
with the increase of invert. Many fruits, especially 
berries, contain little or no sucrose; in apples, pears, 
peaches, apricots, oranges, plums and pineapples the 
amount is comparatively high. Celluloses, forming the 
fiber content, are of course a considerable carbohydrate 
part of some fruits. Pectose is found combined as 
pectocellulose in the lamellae of cell walls. When hy- 
drolyzed with dilute acids or alkalies, or by pectase, an 
enzyme present in ripening fruit, pectose changes to 
pectin. The former is insoluble in water, and may be 
decomposed into a number of substances known as 
pectinic acids, usually found combined with calcium. 
The term pectinase is applied to the enzyme which coag- 

^ Fruits and Fruit Products, Bull. 66, U. S. Dept. Agric, Div. 
of Chem. 

Bull. 28, Atwater and Bryant, Idem. 
9 



124 house:hoi.d chemistry 

ulates the juices containing the dissolved pectinous sub- 
stances, forming the so-called fruit jellies.^ 

This reaction is conditioned on the presence of lime, 
and the establishment of a certain equilibrium between 
the enzyme and the concentration of the fruit acid and 
the calcium salts. Fleshy roots and fruits — carrots, tur- 
nips, apples and pears — are especially rich in pectocellu- 
loses, but many other fruits, e. g., currants, possess con- 
siderable amounts. Preparations of pectose from vege- 
table sources for jelly making are now on the market. 

In unripe fruits there is often much tannin, which dis- 
appears as the fruit ripens. 

Acidity. — The acidity of most fruits is due to mix- 
tures of organic acids and acid salts, such as acid potas- 
sium tartrate. Citric, malic and tartaric acids are often 
present, and may be determined separately. However, 
for convenience, analysts usually express total acidity as 
sulphuric acid. 

Ash Constituents. — In most cases, these show a 
marked alkalinity, and consist largely of carbonates of 
sodium, potassium, calcium, and magnesium. Sulphates 
and chlorides are found only in traces. 

Proteins. — The protein content is inconsiderable, sel- 
dom reaching more than i per cent, in fresh fruit. Much 
of this is insoluble, and appears only in small quantities 
in the expressed juice. As a rule, the presence of more 
than I per cent, of protein in a jelly would indicate that 
gelatin had been used to aid in the gelatinizing of the 
article. 

^ Kraemer : Applied and Economic Botany. 



HOUSEHOI.D CHEMISTRY 



125 



The following table from the Ann. de Chimie et de 
Phys,, Vol. 61, gives comparative figures as to content 
of reducing sugar, sucrose, total sugar and acid in 
various fruits: 



Per cent. 

of 

reducing 

sugar 



Per cent. 

of 

sucrose 



Per cent, 
of 

total 
sugari 



Per cent. 

of acid 

figured as 

tartaric^ 



Hot house grapes ..... 

Dried grapes 

Dried pippins 

Violet figs 

English cherries 

Fresh grapes 

Fresh pippins 

Dried pears 

White heart cherries • • 

Fresh pears 

White currants 

Strawberries 

Dried apples 

English pippins 

Raspberries 

Strawberries (different 

variety) . • 

Oranges 

Queen Claude plums - . 

Mirabelle plums 

Apricots 

Pineapples 

Green grapes 

Peaches 

I^emons 



17.26 
16.50 
12.63 

11.55 
10.00 
9.42 
8.72 
8.42 
8.25 
7.16 
6.40 
5.86 
5.82 
5.45 

5-22 

4.98 
4.36 
4.33 
3.43 
2.74 
1.98 
1.60 
1.07 
1.06 



0.00 
0.00 
3.20 
0.00 
0.00 
0.00 
5.28 
0.36 
0.00 
0.68 
0.00 
0.00 

0.43 
2.19 
2.01 

6.33 
4.22 
1.25 

5.24 
1.04 

11.33 
0.00 
0.92 

0.41 



18.37 
16.50 

15.83 

11.55 

10.00 

9.42 

13.40 

8.78 

8.25 

7.84 
6.40 
5.86 
6.25 
7.64 
7.23 

II.3I 
8.58 

5.55 
8.67 
3.78 
^3.30 
1.60 
1.99 
1.47 



0.345 
0.403 
0.403 
0.057 

o.66r 
0.558 
1. 148 

0.115 
0.608 
0.287 

1.574 
0.750 
0.253 
0.633 
1.580 

0.550 
0.448 
1.208 
1.288 
1.864 

0.547 
2.485 
0.783 
4.706 



1 Quoted by Buegnet. 

2 Quoted by Konig. 

ANALYSIS OF A FRITIT.* 
Water and Total Solids — Weigh out about 20 grams of the 
pulped fresh fruit, or about as much dried fruit as will give 
' Bull. 66, Div. of Chem., U. S. Dept. of Agric. 



126 HOUSDHOI^D CHEMISTRY 

3 or 4 grams of dried residue, place in a weighed flat bottom 
dish, mix with a weighed quantity (4-5 grams) of freshly ignited 
asbestos, add a few cc. of water, mix thoroughly and dry at 100° 
for 20 to 24 hours. Estimate water and total solids. 

Determination of Ash — Thoroughly char the above residue in 
a porcelain or platinum dish at as low a heat as possible, extract 
with water, filter, and wash. Return filter paper and insoluble 
material to the dish and thoroughly ignite ; add the soluble por- 
tion and a few cc. of ammonium carbonate solution, and evapo- 
rate the whole to dryness. Now heat to very low redness, cool 
in a desiccator, and weigh rapidly. The result is total ash con- 
stituents. 

Determination of Alkalinity — Run an excess of N/5 HNO3 
into the dish containing the ash. Add a drop or two of methyl 
orange. Mix carefully with a rubber tipped stirring rod, and 
titrate excess of acid with N/io KOH. Calculate alkalinity as 
potassium carbonate. 

Total Acids. — Dilute 10 grams of fruit juice or pulped fruit 
up to 250 cc, with recently boiled distilled water. In the case of 
fruit pulp boil for a minute or two, to dissolve all acid from the 
fruit cells. Add phenolphthalein and titrate against N/io KOH. 
Calculate as H2SO4. 

Scheme for the Separation and Identification of Malates, 
Citrates, Tartrates, Oxalates and Acetates. — To the filtered fruit 
juice, prepared as in the preceding experiment, add Ca(0H)2, 
preferably in the form of milk of lime, until the neutral point is 
reached. Avoid excess. (If the fruit juice is neutral at the 
start, add CaCL solution as long as a precipitate forms.) Stir 
well, filter and wash. Proceed as follows with (i) residue; 
(2) filtrate: 

I. Residue. (Containing calcium tartrate and oxalate). — 
Treat on a filter with acetic acid. Residue is calcium oxalate, 
soluble in hydrochloric acid. Filtrate contains calcium acetate 
and tartaric acid. Add 95 per cent, alcohol and potassium hy- 
droxide, and shake well. On standing acid potassium tartrate 
appears as well-defined crystals. 



HOUSEHOI.D CHEMISTRY 12/ 

2. Filtrate. (Containing calcium malate, citrate and acetate.) — 
Boil, filter, and wash with hot distilled water. Reserve 
filtrate. Residue is calcium citrate. Treat on filter with dilute 
sulphuric acid. Residue is calcium sulphate. To the solution 
add silver nitrate and dilute ammonia — a white precipitate of 
silver citrate forms which does not blacken on boiling. The 
reserved filtrate contains calcium malate and acetate. Concen- 
trate, cool, and add to a large excess of ethyl alcohol. Filter and 
wash. Residue, calcium malate. Solution, calcium acetate. To 
this add sulphuric acid and heat. Note odor of ethyl acetate. 

Determination of Nitrogen — Use 5 grams of fruit jelly, or 
10 grams of fresh juice or fruit. Follow the Kjeldahl method 
described in Chaper XVI. Use 6.25 as the nitrogen factor. 

Determination of Carbohydrates — (a) Reducing Sugar. — 
Treat 25 grams of fruit juice or pulp with basic lead acetate 
in excess (2 to 5 cc), make up to 100 cc and filter. Transfer 
from 25 to 50 cc. — depending upon the percentage of reducing 
sugar present — to a 100 cc. flask and add a saturated solution 
of sodium sulphate in sufficient amount to precipitate the excess 
of lead; complete the volume to 100 cc, filter, and determine 
reducing sugar by Allihn's method. (See Chapter XVI.) 

(&) Cane Sugar. — When only a small amount of cane sugar 
is present, it is best determined by calculation from the increase 
in reducing sugars after inversion. Treat double the amount 
of fruit or juice used in (a) with basic lead acetate, make up 
to 100 cc, filter, and invert 50 cc. in a 100 cc. flask with 5 cc 
of hydrochloric acid. (See Chapter XVI.) After inversion 
nearly neutralize the acid with sodium hydroxide, precipitate 
the excess of lead with sodium sulphate, and dilute with water 
to 100 cc Filter and dilute so that the solution does not con- 
tain more than i per cent, of reducing sugar. The per cent, 
of increase in reducing sugar after inversion, multiplied by 0.95, 
equals the per cent, of cane sugar. 

Pentoses and Pentosans.— Fifr/wra/ Te^^— Place 25 grams of 
the fruit juice, diluted to 100 cc, in an Erlenmeyer flask, add 
HCl of 1.06 specific gravity and boil. Hold in the vapor a filter 



128 HOUSEHOI.D CHEMISTRY 

paper moistened with a solution of equal parts of anilin and 
50 per cent, acetic acid. A bright red color appears on the 
paper if more than traces of furfural are present/ 

Dextrin. — A qualitative test may be made by decolorizing the 
diluted fruit juice with boneblack, and observing the color re- 
action with iodine. Another method of decolorizing consists in 
bringing the solution nearly to the boiling point, then adding sev- 
eral cubic centimeters of dilute (i to 3) sulphuric acid and 
gradually potassium permanganate. Stir until the color disap- 
pears. 

Alcohol Precipitate. — If alcohol is added in excess to a solu- 
tion of a fruit product, such as a jelly, a flocculent precipitate 
may form with no turbidity, indicating a pure fruit product. A 
white turbidity appearing at once, followed by a thick, gummy 
precipitate, shows the presence of glucose. In fresh fruit juices 
there is often marked turbidity which is caused by the starchy 
matters present. 

Bxperiment in Jelly-Making. — To determine the optimum con- 
ditions for gelatinizing fruit juices, treat cranberries, apples, cur- 
rents, and other jelly-making fruits as follows: 

1. Express the juice from the raw fruit and allow a portion 
to stand. Is there gelatinization in any case? 

2. Bring another portion to a boil. Cool and observe. 

3. Boil other portions for measured periods, increasing in 
duration. What is the relation of time to jelly formation? 

4. Repeat (2) and (3), adding an equal bulk of sugar to the 
fruit juice at the boiling point. 

5. Repeat (2), (3) and (4), modifying as follows: 

(a) Heat the fruit until the skins burst, and express the juice. 

{h) Boil the fruit for 5 minutes and express the juice. 

Isolation of Pectin — Grate fresh white turnips and extract all 
solubles with cool distilled water. Macerate the extracted residue 
with cold dilute HCl (1:15) for 48 hours, pour off the liquid 
and precipitate pectose bodies by adding an equal bulk of ethyl 
alcohol. 

* See Sherman : Organic Analysis. 



CHAPTER IX. 



FATS. 



Fats and oils are widely distributed in vegetable and 
animal forms of life. The line of distinction between 
a fat and an oil is not closely drawn, but fats are gener- 
ally found as solids at about 20° ; oils as fluids. True 
fats and oils are esters, in which the base is always 
glycerol, although the fatty acids vary. They are there- 
fore glycerides, the type formation of which is repre- 
sented by the equation: 



C3H,(OH)3 + 3C,,H3,COOH 

glycerol stearic acid 

(C„H3,COO)3C3H, + 3H,0. 

glyceryl tristearate 
or stearin 

As found in nature, fats are not simple glycerides, 
but mixtures of two or more. For instance, from mut- 
ton and beef fat, a distearopalmitin, a dipalmitostearin 
and a dipalmito-olein have been separated.^ 

The principal fatty acids represented in these mixed 
fats are: 

^ Leathes : The Fats. 



I30 



HOUS^HOIvD CHEMISTRY 



Saturated Acids. 

Butyric, CsHtCOOH 
Caproic, CsHuCOOH 

Caprylic, CtHisCOOH 
Capric, CsHxqCOOH 
Laurie, CUH23COOH 

>Iyristic, CigH^TCOOH 

Palmitic, C15H31COOH 

Stearic, CnHssCOOH 

Unsaturated Acids. 
Oleic, C17H33COOH 
L,inoleic, CnHsiCOOH 



Occurrence. 

Chiefly in butter. 

In butter (1.2 per cent.) ; in 
coconut and palm oils." 

Same as caproic. 

Same as caproic. 

Milk (trace) ; coconut and lau- 
rel oils. 

Milk (trace) ; lard, codliver oil, 
nutmeg butter. 

In most animal and vegetable 
fats, e. g., palm oil, butter, 
lard. 

In most fats, especially solid 
forms. 

In most fats and oils. 

Linseed oil. This or a similar 
acid also in other vegetable 
oils, including cotton seed. 

Since the fatty acids exist as liquids, semi-solids and 
solids, the predominating acid or acids in a fat deter- 
mine its character in this respect. 

Chemically, the glycerides take their name from their 
fatty acid, combined with the suffix ^'in" — thus, stearin, 
palmitin, olein, etc. 

Properties of Fats. — Solubilities. — ^With few exceptions, 
fats are practically insoluble in cold water and alcohol, 
sparingly soluble in hot alcohol, but dissolve readily in 
light hydrocarbons such as petroleum ether and gasoline. 
All fats are soluble in ether, chloroform, carbon tetra- 
chloride and benzene. 

Odor and Taste. — Pure neutral glycerides are nearly 



HOUSEHOLD CHEMISTRY I3I 

all odorless and tasteless. An exception is butyrin, 
found in butter, which contains soluble butyric acid. 
The smell and taste of natural fats and oils are due to 
foreign substances, such as ethereal oils. 

Non-volatility. — Fats and oils are non-volatile, there- 
fore are called fixed, in contradistinction to the ethereal 
oils. A result of this property is the formation of grease 
spots. 

CrystalUnity. — Fats are crystalline; the crystals of 
pure fats form a means of identification. 

Melting and Solidifying Points. — In passing from the 
solid to the liquid state fats do not alter in composition. 
The melting and solidifying points of fats are definite 
unless the mixture is complicated. The solidifying points 
of oils range from a few degrees above zero to about 
—28°. 

Specific Gravity. — Most oils and fats have a specific 
gravity ranging from 0.910 to 0.975 ^^ 15.5°. 

Effect of Heat. — On prolonged heating in contact 
with air, or heated above 250°, fats and oils decom- 
pose, with formation of volatile products, notably acro- 
lein. Acrolein is a decomposition product of glycerol: 

less 2H2O 

CH,OH.CHOH.CH,OH •-- CH,:CH.CHO. 

glycerol acrolein 

It has a peculiar irritating odor characteristic of burning 
fat, and its formation is a simple means both of identi- 
fying the presence of a fat and distinguishing between 
a true fat or oil and a hydrocarbon. 



132 HOUSEHOLD CHEMISTRY 

Bmulsification. — This is a physical change brought 
about by agitating a fat in the fluid state with some emul- 
sifying agent such as egg albumin or soap solution. The 
fat is broken up into tiny globules which are coated with 
the tenacious medium and thus prevented from coal- 
escing. Emulsions are more or less temporary, as in the 
case of mayonnaise, or the fat in freshly drawn milk, or 
permanent as in certain commercial preparations. Bmul- 
sification increases the area for chemical action in soap- 
making and fat digestion. 

Drying Oils. — Three classes of oils are recognized: 
Non-drying, semi-drying, and drying. The distinctions 
are made according to their tendency to form a dry, 
elastic film on exposure to the air. The drying prop- 
erty in an oil is due to the presence of unsaturated fatty 
acids, which readily become saturated by combination 
with oxygen. Linseed oil is an example of an oil which 
quickly undergoes oxidation and is converted into a 
varnish. In this case drying is greatly hastened by a 
previous boiling of the oil. 

Iodine Value. — The degree of unsaturation in a semi- 
drying or drying oil can be determined by the amount of 
iodine it will take up in the formation of addition prod- 
ucts. This is known as the iodine number or value of 
the oil. 

Hydrogenation. — By a process comparatively new, 
fats and oils containing unsaturated fatty acids are made 
to take up hydrogen by catalytic action and become sat- 



house:hoi.d chemistry 133 

urated compounds. Such fats are now being put on the 
market for edible purposes and for soap-making. 

Hydrolysis. — The hydrolysis of fats, as well as of 
esters in general, is called saponification. The change is 
a splitting of the fat into its components — glycerol and 
fatty acids — illustrated by the reaction: 
(C,,H3,COO)3 C3H, + 3HOH «- 

stearin 

3C„H,,C00H + C,H,(OH),. 

stearic acid glycerol 

Moisture alone will not effect hydrolysis of fats in any 
definite length of time: a catalyst is necessary to accel- 
erate the change. Heat, acids or alkalies, and enzymes 
act as catalytic agents. At a temperature of 200° or 
more, water, e. g., superheated steam, attacks glycerides. 
If dilute HCl or H2SO4 is used, the saponification occurs 
rapidly with less heat. Quick hydrolysis is also brought 
about by heating the fat with an excess of an alcoholic 
solution of caustic soda or potash. In this case the fatty 
acid set free units with the alkali to form soap (see next 
page, and Chap. XV). If fat-splitting enzymes are pres- 
ent, hydrolysis may be brought about by moisture at nor- 
mal temperatures. These enzymes occur in seeds contain- 
ing vegetable oils, and during germination are active in 
changing the fat to a form utilizable by the embryo. As 
the quantity of enzymes in the filtered commercial oils 
is small, the per cent, of free fatty acid they contain is 
likewise small as a rule, and hydrolysis does not proceed 
if they are protected from air and moisture, or are not 
in contact with the organic material from which they 
have been extracted. Under the reverse conditions the 



134 HOUSEHOLD CHE:MISTRY 

formation of free fatty acid may proceed to a consider- 
able degree even in refined oils. 

Rancidity. — Although a fat or oil may have an acid 
reaction, it is not necessarily rancid — the terms are not 
synonymous. Acidity precedes rancidity; the change to 
the latter state is supposed to be due to oxidation of free 
unsaturated fatty acid by the oxygen of the air, in the 
presence of light. The peculiar taste of rancid fat is 
caused by these oxidation products. Bacterial action is 
not necessary to the change, for a sterile fat may become 
rancid, but the presence of foreign substances may favor 
enzyme or bacterial hydrolysis of the glycerides. Butter 
for this reason easily becomes rancid, as some protein 
material may be present. A high olein content predis- 
poses to rancidity hence olive and similar oils should be 
protected from contact with air and direct sunlight. 
' Soap-Making Property. — Fats being esters are partic- 
ularly susceptible to hydrolysis. When this is accom- 
plished through the agency of metallic hydroxides, the 
separated acids combine with the bases to form a class of 
substances, usually described as soaps. Only the potash 
and soda compounds are soluble in water and possess 
detergent properties. The insoluble soaps find various 
commercial uses as lubricants, paints and in dyeing op- 
erations. 

By the use of NaOH the changes are as follows : 

(1) {C,,lI,fiOO\C,U, + 3HOH ^ 

3C,,H3,COOH + C,H,(0H)3. 

(2) Ci,H3,C00H -j-NaOH ^ C^.H^^COONa + HOH. 

sodium stearate 
or hard soap. 



HOUSEHOLD CHEMISTRY I35 

The sodium salt forms a hard mass which deliquesces 
and becomes harder on exposure to air. The potash 
compound separates as a soft mass which deliquesces in 
air to a jelly-like substance. These characteristic proper- 
ties are commonly expressed by the terms hard and soft 
soap. 

Soluble salts of lime combine with soda or potash soaps 
to form the insoluble lime soap (Ci7H35COO)2Ca (cal- 
cium stearate), the usual type reaction with soap in hard 
waters. 

EXPERIMENTS ON FATS. 

"Ultimate Composition — Hydrogen and Oxygen in the Form of 
Water. — Heat 20-25 drops of clear olive oil in a clean dry test 
tube. Note the watery deposit in the cooler part of the tube; 
some of this running back will cause the fat to crackle. 

Glycerin. — Continue heating the tube until dense fumes arise 
from the boiling liquid. These are due to acrolein, CH2 : CH.CHO, 
a decomposition product of glycerin. Note the odor and explain 
the presence of glycerin. 

Carbon and Hydrogen as Hydrocarbons Resulting from the 
Breakdown of the Fatty Acids. — Pour the cold tube contents 
into a clean dry porcelain dish and heat slowly but strongly over 
a low flame. Note the gradual darkening of the liquid due to 
freeing of carbon and the tarry coat on the rim of the dish 
(hydrocarbons). At this point hold a lighted match over the 
dish and note the inflammable character of the vapor (hydro- 
carbon gases). Extinguish the flame and continue the heating 
until only a black residue remains. This is carbon; prove it by 
burning off. 

Extraction of Pure Fat from Animal Sources.. — Weigh 10 
grams of beef suet cut up in small pieces. Place them in a 



136 house:hoIvD chemistry 

small evaporating dish and heat over hot water until translucent. 
Then strain through muslin into a porcelain dish, squeeze out the 
cloth and reserve the liquid for tests on fats. 

Transfer the residue to a small mortar, add 10 cc. of strong 
alcohol, grind well. Pour this mixture into a small flask, wash 
out the mortar with more alcohol and add the washings to the 
flask. Finally close the flask with a cork bearing a condenser 
tube 24 inches long, support on a ring stand over a water-bath 
and heat for a few minutes. Remove from the heat and when the 
suspended matter has settled, uncork the flask and pour the clear 
liquid on a small filter, allowing the filtrate to run into a large 
test tube. To the residue in the flask, add 20 cc. of ether, insert 
the cork and condenser and cautiously heat in warm water until 
the liquid boils. Then transfer the entire contents of the flask 
to a small filter and collect the filtrate in the same tube as be- 
fore. Close the test tube with a loose cotton plug and allow 
it to stand until crystals deposit from the liquid. Examine these 
under the microscope and draw a diagram of them. Wash the 
residue from the last filtration with a little ether, squeeze out, 
'spread on the muslin and dry. Take it up with a little water, 
add a few drops of Millon's reagent, and heat gently. A red 
color indicates protein matter. 

Make the following tests on the rendered (extracted) fat: 

1. Solubility. — Test the solubility of small portions of fat in 
separate test tubes containing cold water, cold alcohol and cold 
sodium carbonate solution. Cautiously heat all to boiling. Re- 
cord and compare the results. 

2. Absorption. — Place a small piece of fat on a filter paper and 
heat until the fat melts ; note the result and compare with hydro- 
carbons. 

3. Formation of Acrolein. — Rub a small piece of fat in a mor- 
tar with some acid potassium sulphate, transfer the mass to a 
clean, dry test tube and heat cautiously; note the peculiar dis- 
agreeable odor of acrolein and the reducing effect of the aldehyde 



HOUSEHOLD CHEMISTRY I37 

on a strip of filter paper moistened with ammoniacal silver ni- 
trate. 

4. Bmulsification. — Shake together a few cc. of codliver oil 
and dilute sodium carbonate. Notice the resulting white mass 
which is called an emulsion; what well-known liquid is similar 
in appearance? Examine two or three drops of this emulsion 
under the microscope and note the character of the compound. 

Repeat the experiment, using a few drops of olive oil and a 
solution of albumin. 

5. Saponification with Alkali. — To about i gram of fat in a 
low flask fitted with a reflux condenser add 25 cc. of alcoholic 
potash solution, and boil. Replace the liquid lost by evaporation 
with alcohol. As the heating progresses, the mixture should 
become homogeneous ; if it does not, add a little more potash and 
boil until clear (saponified). Remove the cover and evaporate 
the bulk of the alcohol, finally adding hot water and heating 
until all alcoholic odor has disappeared. Cool the liquid, divide 
into three parts and use in (6) and (8). 

6. Precipitation and Decomposition of Soap. — To one portion 
add a saturated solution of salt. Notice the curdy precipitate 
(soap). Filter off this precipitate, try its solubility in cold water. 
Repeat the test using strong caustic soda in place of salt. Acidify 
another portion of the dissolved soap with dilute sulphuric acid. 
Note the curdy precipitate (fatty acids). Boil the mixture until 
clear, filter and use in test 7. 

7. Test the solubility of the fatty acids in water, alcohol and 
sodium carbonate solutions. Record results and compare with 
the esters. 

8. Formation of Lime Soap. — ^Add an excess of a solution of 
calcium chloride to another portion of the soap liquid and notice 
the greasy precipitate of calcium stearate which is insoluble in 
^warm water and alcohol (Hme soap, produced by hard waters). 



138 HOUSEHOIvD CHEMISTRY 

9. Determination of Free Patty Acid. — Take a weighed amount 
of olive oil (about i gram), add about 25 cc. of alcohol which 
has been neutralized with N/NaOH (one drop will probably be 
sufficient) and boil. While hot, titrate against N/io NaOH. 
Calculate the percentage of fatty acid in the sample in terms of 
oleic acid- 
ic. Koettstorfer Number. — Weigh out 2.5 grams of fat in a 
low flask. Add 25 cc. of approximately N/4 alcoholic potash 
solution, cover with a watch glass and heat on a water-bath until 
the fat is completely saponified. Cool, and titrate back excess 
of alkali with N/2 HCl. Make a blank test in a similar manner 
on the alcoholic potash and calculate the per cent, of alkali 
absorbed in saponification. This test is used in the case of an 
unknown fat to determine its combining ratio with alkali. 

11. Iodine Test. — Into each of two test tubes pour 20 drops of 
the oil under test. Dissolve the oil with about 5 cc. of chloro- 
form. Add 4 or 5 drops of iodine solution to one of the samples ; 
cork and shake. To insure an excess of iodine, test by placing 
I drop of the mixture on filter paper. Observe the change in 
color in the tube to which iodine has been added, in case the oil 
contains unsaturated fatty acids. 

12. Bxtraction of Pats from Cereals or Nuts. — Grind the 
sample to a fine powder and dry in an air bath at ioo°-io5° to 
constant weight. Weigh from 2 to 3 grams of the dried material, 
place in an extraction shell, and cover loosely with absorbent 
cotton. Extract in a Soxhlet apparatus with water-free ether 
for about 16 hours, allowing the extract to run into a weighed 
flask. Use a water-bath, or better, an electric plate, to avoid 
danger from overheating the ether. Finally evaporate the con- 
tents of the flask to constant weight and estimate the per cent, 
of fatty material removed in the ether extract. 

13. Special Tests for Cottonseed Oil — (a) Becchi's Test. — To 
5 cc, of the oil in a 6-inch test tube, add an equal volume of 



HOUSEHOLD CHEMISTRY I39 

silver nitrate dissolved in alcohol (i per cent, solution) ; close 
the test tube with a cotton plug and keep it in boiling water for 
10 to 15 minutes. A darkening of the mixture indicates cotton- 
seed oil. The acids in cotton-seed oil quickly reduce the silver 
nitrate; those in olive oil only after some time. 

(b) Halphen's Test. — To 5 cc. of the oil in a 6-inch test tube 
add 5 cc. of amyl alcohol and 5 cc. of carbon disulphide contain- 
ing a little free sulphur. Close the test tube with a loose cotton 
plug and keep in hot water away from an open flame for % hour. 
A red coloration indicates cotton-seed oil. This is a very deli- 
cate test. 

BUTTER. SPECIFIC TESTS. 

Wash a teaspoonful of melted butter in several waters until 
free from salt. Prove this by making the silver nitrate test on 
the last washing. Note any difference between the first and last 
washings when tested with litmus paper. Explain. Cool and dry 
the washed butter between filter paper, melt, and dissolve in 
gasoline. Filter the resulting solution and wash the residue on 
the paper with gasoline until a drop of the washings evaporated 
on paper leaves no greasy stain; dry and note the character of 
the residue (curd). Moisten with Millon's reagent, heat and 
note result. 

Spoon Test — Gently heat a piece of butter about the size of 
a cherry in a tablespoon. If it froths without spattering, it is 
pure butter. If it foams and spatters it is renovated butter; if 
it spatters only, it is oleomargarine. 

Butyric Acid Test — In a 4-ounce narrow neck flask, fitted with 
a one-holed rubber stopper, put about 2^ grams of butter. 
Saponify with caustic potash. Decompose the resulting product 
with dilute sulphuric acid in excess. Then distil the product 
gently, using a bent tube condenser. Butyric acid will distil at 
about the temperature of boiling water. Allow the distillate to 
drop into a funnel containing moist filter paper. This causes 
10 



I40 HOUSEHOLD CHEMISTRY 

the retention of fatty acids (other than butyric). Below the 
funnel is placed an Erlenmeyer flask containing distilled water 
made alkaline by adding 2 drops of 10 per cent. NaOH, and 
tinted with phenolphthalein. The disappearance of the pink color 
will occur when sufficient butyric acid has passed over to neu- 
tralize the soda. 



CHAPTER X. 



PROTEINS. 

The proteins are the chief nitrogenous constituents of 
both plants and animals. Owing to their complex nature, 
the exact chemical structure of protein bodies has not 
been determined, but they are regarded as anhydrides of 
amino acids, since they yield these acids on hydrolysis. 

The elementary composition of all proteins includes 
carbon, hydrogen, oxygen and nitrogen, with sulphur in 
typical forms. These elements are found in the follow- 
ing average ratio: Carbon 51-55 per cent., hydrogen 7 
per cent., nitrogen 15-19 per cent., oxygen 20-30 per 
cent., sulphur 0.4-2.5 per cent. In addition, phosphorus 
is frequently found in direct or indirect combination 
with the protein molecule, and iron and calcium appear 
in some cases. 

The large size of the protein molecule can be judged 
by the formula assigned to globin, one of the simplest 
forms : C726H1174N194S3O214. 

Classification. — Proteins are classified principally on 
the basis of differences in solubilities and hydrolysis. 
The classification which follows is the one recommended 
by the American Physiological Society and the American 
Society of Biological Chemists : 



142 



HOUSEHOLD CHEMISTRY 



Simple 



Proteins <{ Conjugated 



Non-proteins 



Derived 



' Extractives 
Amides 
Amino acids 



' Albumins 
Globulins 
Glutelins 
Alcohol 

Solubles 
Albuminoids 
Histones 
Protamines 

' Nucleoproteins 
Glycoproteins 
Phosphopro- 

teins 
Haemoglobins 
Lecithoproteins 

Primary 
derivatives 



Secondary 
derivatives 



Proteans 
Metaproteins 
Coagulated 
proteins 

{Proteoses 
Peptones 
Peptides 



In this classification the group called simple proteins 
hydrolyze to amino acids, conjugated proteins yield pro- 
tein decomposition products and some other body. This 
latter substance is nuclein in the nucleoproteins, a car- 
bohydrate in the glycoproteins, a phospho body in the 
phosphoproteins, haematin in haemoglobins, and a fatty 
substance in lecithoproteins. The derived proteins are 
changed forms produced by the action of heat, acids or 
alkalies, or enzymes. 

Occurrence and Solubilities, — Albumins. — In plant and 
animal bodies, such as Qgg, plant, lact and serum albu- 
mins. Soluble in pure water, precipitated by complete 



HOUSEHOI.D CHEMISTRY I43 

saturation with ammonium sulphate, but not by saturated 
magnesium sulphate or sodium chloride. 

Globulins. — In animal bodies fibrinogen and derived 
fibrin, and myosinogen and derived myosin show glob- 
ulin characteristics. Other forms are egg serum and 
lact-globulin. Examples in plants are legumin and 
edestin. Globulins are not soluble in water or in dilute 
acids, but dissolve in dilute solutions of inorganic salts. 
They are precipitated by saturation with magnesium sul- 
phate or sodium chloride, or by half saturation with 
ammonium sulphate. 

Glutelins. — Found in cereals; as glutenin in wheat 
and oryzenin in rice. Insoluble in all neutral solvents 
but readily soluble in very dilute acids and alkalies. 

Alcohol-Solubles (Prolamines). — Gliadin (in wheat, 
combining with glutenin to form gluten in a dough mix- 
ture) ; zein (maize); hordein (barley). Insoluble in 
water and absolute alcohol, soluble in 70-80 per cent, 
alcohol. 

Albuminoids (Scleroproteins). — Keratins of horn, 
hair, nails, egg membrane; collagen of white connective 
tissue, ossein of bones and elastin of yellow elastic tissue, 
yielding gelatin; silk gelatin and fibroin. Insoluble in 
all neutral solvents. Gelatin, a derived form, dissolves 
in hot water. 

Histones. — Found combined with nucleic acid, form- 
ing certain nucleoproteins, e. g., in the nuclei of blood 
corpuscles of birds, in the thymus gland, etc. Soluble in 
water, insoluble in very dilute NH4OH. 



144 HOUSEHOI.D CHEMISTRY 

Protamines. — Simple in composition; found in con- 
junction with nucleic acid in spermatozoa of certain fish. 
Soluble in water. 

Nucleo proteins. — Widely distributed; form chief pro- 
tein constituent of nuclei ; contain nucleic acid combined 
generally with albumins, histones, or protamines. 

Glycoproteins. — Ovo-mucoid; mucin of mucous mem- 
brane. Soluble in dilute alkalies; mucins reprecipitated 
by acetic acid, mucoids are not. 

Phospho proteins. — Caseinogen of milk, vitellin of ^gg 
yolk. Insoluble in water; readily soluble in alkalies, 
forming salts; precipitated by acids. 

Haemoglobins (Chromoproteins). — Chromogenic sub- 
stances, e. g., haemoglobin in blood. 

Lecitho proteins (I^ipoproteins). — These are nitrogen- 
ous bodies combined with a fat radicle. Examples are 
lecithans and phosphatides. Occur in yolk of ^gg, milk, 
etc. 

Proteans. — Occur as insoluble products apparently re- 
sulting from the incipient action of water, very dilute 
acids, or enzymes. 

Metaproteins. — Found in partial hydrolysis of pro- 
teins by the action of acids or alkalies; known as acid 
or alkali albumin or globulin, etc. Insoluble in water, 
soluble in dilute acids or alkalies, precipitated by alcohol. 

Coagulated Proteins. — See coagulation. 

Proteoses. — Intermediate products of protein diges- 
tion. Soluble in water, precipitated by alcohol or sat- 
uration with ammonium sulphate. 



HOUS^HOIvD CHEMISTRY I45 

Peptones. — Further products of proteolysis. Soluble 
in water and saturated ammonium sulphate. Precipi- 
tated by alcohol. 

Peptides. — Simple hydrolytic products of the protein 
molecule, which readily yield two or more amino acids 
on further hydrolysis. An example is glycyl-glycine 
H^N.CH^.CO.NH.CH^COOH. 

Extractives. — Creatin and creatinin, found in muscle. 

Amides. — Urea, asparagine in asparagus. 

Amino Acids. — Simple decomposition products of the 
proteins. 

Properties. — i. General. — Proteins are bodies of high 
molecular weight, optically active, colloidal, and gen- 
erally colorless. Most proteins are amorphous, but some 
have been obtained in crystalline form, e. g., edestin 
from hemp seed. They are both acid and basic in re- 
action. 

2. Coagulation. — Many proteins, especially albumins 
and globulins, undergo a precipitation known as coagu- 
lation, on heating their aqueous solutions. The chem- 
ical change between the water and the protein is not 
clearly understood. Complete coagulation is only ob- 
tained in slightly acidified solution. Coagulated proteins 
are insoluble, and cannot be reconverted into the original 
protein substance. Different factors affect rapidity of 
coagulation, so that a range of temperature is usually 
given as the coagulation point of any specified protein. 
The hardening effect of alcohol on proteins is a form of 
coagulation. 



146 HOUSEHOLD CHEMISTRY 

3. Curdling. — This term describes a precipitation of 
protein material by acids or certain salt solutions, espec- 
ially observed in the case of milk. The caseinogen in 
milk exists as a soluble calcium caseinogenate, which is 
broken up by the action of lactic or other acids and the 
caseinogen is thrown out of solution — i. e., the milk has 
curdled. The calcium caseinogenate can be precipitated 
by salting out with sodium chloride. 

4. Clotting. — Certain conjugated proteins undergo a 
change properly known as clotting, which occurs only 
through enzyme action. As seen in milk, the caseinogen 
is acted upon by rennin, which produces a soluble hy- 
drolytic product, casein. The lime salt of casein is in- 
soluble, and clotting can take place, therefore, only if 
soluble calcium salts are present to form the insoluble 
calcium caseinate. This is the clot produced in junket 
and cheddar cheese making. A similar change takes 
place in the clotting of the fibrinogen of blood, and, as 
far as is known, in the muscle tubes after death, caus- 
ing rigor mortis. 

5. Hydrolysis. — The hydrolysis of simple proteins 
yields the following as the principal decomposition 
products : 

Protein ••-^ Metaprotein »-»► Proteoses — »- Pep- 
tones »»-*- Peptides »-*► Amino acids. 

Most albumins and globulins also yield a carbohydrate 
substance, which in several cases, e. g., &gg globulin, has 
been identified as glucosamin. 

Phosphoproteins split off an insoluble phosphorus 



HOUSEHOI.D CHEMISTRY 



147 



compound in the early stages of hydrolysis, which be- 
comes soluble later in digestion. To this substance the 
names para- or pseudo-nuclein have sometimes been 
given. 

Nucleoproteins hydrolyze as follows : 



Nucleoprotein 






/ \ 


Protein Nuclein 


/ \ 


Protein Nucleic acid 


/ 


\ 


/ 


\ 


Purin : 


/ 


\ 


Adenin 


/ 






Guanin 


/ 






Hypoxanthin 


Meta phosphoric 


Bases < 


Xanthin 


acid 




Pyrimidin : 


Carbohydrate : 


Uracil 


Pentoses 


Thymin 


Hexo 


ses 




Cytosin 



In the laboratory, complete hydrolysis may be ef- 
fected by boiling with concentrated HCl for 6 to 12 
hours, or with 25-33 P^^ cent. H2SO4 for 12 to 20 hours. 

TESTS ON PROTEINS. 
TTltimate Composition — i. Nitrogen as Ammonia. — Mix some 
dried egg with lime and moisten sufficiently to roll into small 
balls with the fingers. Place two or three of these balls in a dry- 
test tube, heat and hold in the vapors a piece of moistened red 
litmus paper. Note the result. Let the paper dry and observe 
the change. 

2. Sulphur as Hydrogen Sulphide. — Test the fumes with a piece 
of filter paper moistened with lead acetate and note the result. 
The following test is more reliable. Fuse a minute fragment 



148 HOUSEHOI.D CHEMISTRY 

of the dried material in a sodium carbonate bead on wire or 
charcoal, cool, dissolve the melt in warm water in a porcelain 
dish and add a dilute solution of sodium nitroferrocyanide Naa 
Fe(CN)6N0; a purple color indicates sulphur. 

3. Hydrogen and Oxygen as Water. — Observe the condensa- 
tion of water in the cooler part of the tube. 

4. Carbon. — Observe the blackening effect produced by the 
freeing of the carbon. 

5. Phosphorus. — Place the well charred residue in a small 
porcelain dish, moisten with concentrated HNO3 and heat gently 
until excess of acid has been vaporized, then heat strongly until 
the carbon has been entirely consumed. Cool the residue, moisten 
with HNO3, add water, boil and filter if necessary. Test the 
clear liquid with ammonium molybdate. 

For the purpose of making general and specific tests on the 
proteins, a solution of egg albumin prepared according to the 
following directions is recommended. 

ALBUMIN. 

Preparation of Egg Albumin — Carefully break a fresh tgg, 
^llow the clear w^hite to run into a porcelain dish and set the 
yolk aside for future use. Cut the white with scissors or grind 
with sand and place a small portion in a wide-mouthed stoppered 
bottle, add 10 volumes of distilled water, shake until it froths 
and invert over a small casserole of water. When the froth and 
insoluble protein particles float on the surface, carefully with- 
draw the cork and allow some of the liquid to mix with the water 
in the casserole. The liquid will probably be opalescent, due to 
traces of globulin; if strongly so filter through muslin, test the 
fluid with litmus paper and if alkaline neutralize with weak 
acetic acid (2 per cent). 

I. General Tests — (a) Nitric Acid (Xanthoproteic reaction). 
— To a small portion of the filtered liquid, add strong nitric 
acid. This forms a white precipitate which turns yellow on 
heating; now cool and add ammonia — it becomes orange. Com- 
pare with spots on the skin or woolen cloth produced with 
HNO3. 



HOUSEHOI.D CHEMISTRY I49 

(b) Biuret Test. — To i inch of 10 per cent, caustic soda or 
potash, add dilute copper sulphate, drop by drop, until a faint 
blue color but no precipitate remains in the liquid after shaking; 
now add the protein solution. A violet color indicates protein; 
a pink, peptone. 

(c) Precipitation Tests. — Solutions of the proteins are precipi- 
tated by the following reagents: 

Alcohol. 
Tannic acid. 
Picric acid. 

(d) Coagulation by Heat. — Heat some of the fluid to boiling 
and at the same time add, drop by drop, very dilute acetic acid 
(2 per cent.) as long as a precipitate forms; note that this pre- 
cipitate does not appear unless the solution is acid. Attempt to 
filter some of the albumin through a wet filter paper; prove by 
one of the above tests that no protein is in the filtrate. 

2. Special Tests for Albumins and Globulins. — (a) Milton's. — 
To a small portion of the solution, add Millon's reagent and 
heat. This forms a white precipitate which turns red on cool- 
ing, or gives a red color if only a trace of protein is present. 
Avoid using Millon's in the presence of sodium chloride. 

(&) Heller's Test. — Place some strong nitric acid in a test tube 
and allow a solution of albumin to flow gently down the sides 
of the tube; a white ring of precipitated albumin forms at the 
junction. 

{c) Metaphosphoric Acid Test. — Add a solution of albumin 
to a very little cold freshly prepared metaphosphoric acid and 
note the precipitate formed. 

(d) Adamkiewicz' s Test. — Heat the protein solution in a por- 
celain dish with a mixture of i volume concentrated H2SO4 and 
2 volumes glacial acetic acid. A red violet color indicates pro- 
tein. Gelatin does not give this reaction. 

(^) Precipitation Tests. — To portions of the 'solution in sepa- 
rate test tubes add: 



150 HOUSKHOI.D CHEMISTRY 

Acetic acid and potassium ferrocyatiide. 
Mercuric chloride. 
Lead acetate. 

3. Separation Tests — (a) To a portion of the solution, add an 
excess of dry crystallized ammonium sulphate, shake vigorously. 
Albumin and globulin will be precipitated, probably in a changed 
form. Filter through a good grade of paper and make biuret 
test. 

(b) To a portion of the solution, add dry sodium chloride or 
magnesium sulphate to saturation. Globulin is precipitated. 
Filter, and test filtrate with either nitric acid or Heller's test. 
This is a somewhat imperfect method of separating albumin and 
globulin. 

4. Indiffusibility — Place some of the solution in a dialyzer of 
parchment paper and suspend the whole in a beaker of distilled 
water. Test the water subsequently for chlorides with silver 
nitrate and also for protein by the biuret test. 

5. Proteolysis — (a) Acid Metaprotein.— To undiluted egg 
white add concentrated HCl; note the copious precipitate of 
albumin (coagulated). Heat gently until the mass dissolves re- 
sulting in a violet solution. Cool some of this liquid, testing 
separate portions as follows : 

1. Heat to 70° by placing the test tube in hot water and rais- 
ing the temperature gradually. Does any coagulation appear? 

2. Neutralize with dilute caustic soda, filter and make the biuret 
test on the residue. 

3. Add a few drops to 15-20 cc. saturated sodium chloride. 

4. Add a few drops to 15-20 cc. 95 per cent, alcohol. 

(b) Alkali Metaprotein. — Treat undiluted white of ^gg with 
strong alkali; note the clear jelly-like mass which results. Heat 
to clear solution and dilute some of this with water. Make the 
following tests : 

1. Heat to 70°, as above. 

2. Neutralize with dilute acetic acid, filter and make the biuret 
test on the residue. 



house:hoi.d chemistry 151 

3. Add a few drops to 15-20 cc. saturated sodium chloride. 

4. Add a few drops to 15-20 cc. of 95 per cent, alcohol. 

Note. — ^Weaker solutions of albumin are converted to meta- 
protein by treating with a few cubic centimeters of very weak 
alkali or acid (o.i per cent.) at about 40° for several hours. 

Proteose and Peptone — The action of pepsin is hydrolytic and 
produces both proteose and peptone — a case similar to the pro- 
duction of dextrin and glucose from starch. Make a pepsin 
digestion experiment as follows: 

Coagulate egg albumin by heat. Cut into small wedge-shaped 
pieces, put into 3 test tubes and treat as follows : 

1. Cover with highly dilute hydrochloric acid (0.2 per cent.). 

2. Add a small amount of neutralized pepsin solution (o.i per 
cent.). 

3. Add a mixture of equal parts of pepsin and hydrochloric 
acid. 

Place all 3 tubes in a beaker of cold water, heat to body tem- 
perature and note the time they take to clear; also observe 
whether the mass swells ; finally filter all three and test the clear 
filtrates for peptone by the biuret test. 

GLOBTJLIN. 

Globulin from the White of Bgg. — Saturate some of the un- 
diluted solution with dry magnesium sulphate, grinding the 
mass in a mortar. Observe the precipitate of globulin, filter 
and test the filtrate for protein. Now pour water through the 
insoluble mass on the filter and test the extract for proteins. 
Explain. The yield of globulins obtained from this source is 
very small and the following method is preferable: 

Globulin (Bdestin), from Hemp Seed. — Extract dry, ground 
hemp seed with sufficient 5 per cent, solution of sodium chloride 
to cover it well, first grinding the mass in a mortar, then heat- 
ing it for about half an hour at 60°. Keep the mixture at this 
temperature and proceed as follows : 

I. Filter a portion into a warm test tube, through a filter just 
previously washed with hot 5 per cent. NaCl. Notice the clear- 



152 house;hoi.d chemistry 

ness of the filtrate. Cool under running water and observe the 
precipitate of crystallized edestin. Filter off a portion and 
observe the crystals under the microscope. Warm the remainder 
gently, and cool again. What happens? 

2. Learn the solubilities of edestin by filtering a few drops of 
the clear solution as in (i) into (a) water, (b) alcohol, (c) satu- 
rated NaCl, (d) 5 per cent. NaCl (all at 60°). 

3. Filter, and heat gently over hot water until coagulation oc- 
curs. What is the coagulation temperature? 

4. Make biuret and Heller's tests on the clear filtrate. 

GLITTELINS AND AICOHOL SOLUBLES. 
Preparation of Glutenin and Gliadin (page 143) from Gluten 
of Wheat — Take 25 grams of white bread flour, mix on a 
porcelain or glass plate with the least amount of water to make 
a stiff dough (12-15 cc). Do not handle the dough with the 
fingers, use a flexible steel knife. Allow the mass to stand one- 
half hour covered. Then transfer the dough to a well-washed 
and moistened piece of muslin, taking care to clean the mixing 
surface and knife thoroughly; tie up the muslin in the form of 
a bag and wash under a gentle stream of cool water, manipulat- 
ing well with the fingers. Continue the washing until the liquid 
runs clear from the bag, and fails to give the test for starch 
with iodine. The washings from the gluten will yield wheat 
starch by subsidence. Squeeze out as much water as possible 
from the bag, untie it, collect and weigh the moist gluten. Treat 
a small portion of the gluten with 75 per cent, alcohol as long 
as anything is dissolved. The insoluble residue consists of 
glutenin. Try the solubility in very dilute acid and alkali. The 
alcoholic liquid contains gliadin; separate this by liberal dilution 
with water and filtration. Test both the glutenin and gliadin 
with HNO3, Millon's reagent, etc. 

Gelatin. 

By prolonged boiling with water gelatin is produced 
from collagen, which is a protein occurring in the con- 



house;hoi.d chemistry 153 

nective tissue. The sources of both glue and gelatin are 
skin, bones, hoofs, hides, etc., but the latter should differ 
from glue both as to the condition of the raw material 
and the care used in the processes of manufacture. 

The following is recommended as a satisfactory- 
method of preparing gelatin: 

Procure raw shin bones of beef and have them well scraped 
and sawed into i-inch sections. Treat these sections for 2 or 3 
hours, under slight pressure, in a soup digester with the least 
possible amount of water. Pass the extract through cheese- 
cloth, filter into a tall glass cylinder, and when thoroughly cool, 
remove the layer of fat. The jelly-like mass remaining is gela- 
tin. Dry a portion at low temperature and note the result. 

TESTS. 

Heat the balance of the jelly to boiling. What happens? 
Partially cool the liquid, divide into ten parts and test as fol- 
lows : 

1. Dilute hydrochloric acid. 

2. Alcohol. 

3. Acetic acid or lemon juice. 

4. Picric acid. 

5. Acetate of lead. 

6. Salt and tannin. 

7. Heller's test. 

8. Biuret test. 

9. Adamkiewicz's reaction. 

10. Boil a water solution of gelatin for some time. Cool, and 
test its gelatinizing power. Gelatin is hydrolyzed by prolonged 
boiling, and will not gelatinize. 

To estimate the quality of commercial gelatins, make the fol- 
lowing tests : 

I. The amount of ash should not exceed 2 per cent. Burn a 
weighed sample to ash of constant weight and estimate the 
amount. 



154 HOUSEHOIvD CHEMISTRY 

2. Soak samples 4 hours, then make into a jelly by heating. 
Note odor : it should not be offensive. Expose a 5 per cent, 
solution to the air 2 days. Note odor. 

3. Test gelatinizing power by comparing the firmness of jelly 
made by different samples under the same conditions. 

4. Make comparative biuret tests. The color should be violet. 

5. Make Millon's test. There should be little or no response. 

6. Try litmus paper reaction. It should not be alkaline. 

The average composition of bone can easily be shown 
by the following simple experiments : 

1. Boil a piece of raw bone for several hours under pres- 
sure in water, pour off the liquid and allow it to cool. Dry the 
bone residue, observe its porous condition, then break off a small 
piece, pulverize it and dissolve the fragments in hot dilute HCl. 
Boil off the excess of acid, dilute and test the resulting liquid 
for phosphates and calcium. Test the original watery liquid for 
protein. Does it contain gelatin? 

2. Soak raw bone in 10 per cent. HCl for several days. Re- 
move the residual bone from the acid liquid, observe its peculiar 
flexible character. Break off a small piece and test for protein. 
Evaporate the acid liquid to dryness, ignite gently, take up with 
a little HCl, dilute with water and test for phosphates and 
calcium. 

Compare the results of the two experiments and explain the 
action of hot water and cold, dilute acid on bone. 

Examination of Commonly Occurring^ Protein Foods. — 

Analysis of Bggs. — The previous work done on albumin 
(page 148) will suffice for the white of the tgg. The 
yolk should be treated as follows : 

Separation of Fat and Vitellin — Place one-half the yolk of a 
fresh egg in a broad 6-inch test tube, add twice its bulk of 95 
per cent, alcohol, cork, shake vigorously, and place in water at 
55° to 60°. When the mixture has separated into layers, decant 
the clear upper layer through a filter into a clean porcelain dish, 



HOUSEHOI.D CHEMISTRY 1 55 

and treat as in (i). Repeat the extractions until the residue 
in the tube is nearly white. Finally transfer it to a filter, wash 
with another portion of warm alcohol, and dry over warm wa- 
ter. The granular mass resulting is principally vitellin. Treat 
as in (2). 

(i) Pai. — Evaporate the alcohol extract over hot water until 
no odor of alcohol remains. Note the yellow liquid oil. Take a 
portion and test for a fat. Add a few drops of HNO3 to the 
remainder and burn to ash; divide the ash in two portions and 
take up with a few drops of concentrated HCl and HNO3 respec- 
tively, add a httle water to each and heat. Filter if necessary, 
test the HCl portion for iron with ammonium thiocyanate and 
the HNO3 portion for phosphoric acid with ammonium molyb- 
date. 

(2) Vitellin. — Mix thoroughly with 5 per cent. NaCl solution, 
keeping the mixture at 60° for 15 minutes. Filter a few drops 
into 

(o) A large bulk of water made faintly acid with acetic 

acid. 
(&) 95 per cent, alcohol, 
(c) Saturated salt solution. 
What are the solubilities of vitellin? 

Heat another portion of the filtrate to coagulating point. 
What is it? 
Make the nitric acid or Heller's test on another portion. 
Shell — I. Examine a portion of the shell under the low power 
of a microscope; note the physical character. Treat a portion 
of the shell with silicate of soda solution (10 per cent.) ; when 
dry examine as before. (Silicate of soda is used for preserving 
eggs.) 

2. Crush and grind the shell, thoroughly extract with warm 
water, dissolve the extracted mass with dilute hydrochloric acid. 
Note the effervescence. Hold in the fumes a drop of limewater 
on the end of a glass rod and note the clouding. What gas is 
formed? Filter the HCl solution and make slightly alkaline with 
ammonia, add ammonium oxalate and note the white precipitate 
II 



156 HOUSEHOI.D CHEMISTRY 

of calcium oxalate, insoluble in acetic acid. From the data 
found give the composition of the shell and the changes which 
have taken place. 

3. Allow an egg to stand in strong vinegar for several hours, 
remove, wash in one change of water, and note the peculiar con- 
dition of the egg. Examine the acid liquid as in the preceding 
experiment. 

4. Examine equal portions of the yolk and the white of egg, 
separately, for sulphur by mixing with lime and testing with the 
lead acetate method given under proteins. Which do you think 
contains the greater amount of sulphur? 

5. Weigh an egg accurately and repeat the weighing for five 
or six succeeding days. Record the results and explain. 

For the average composition of the egg, see Sherman: Food 
Products. 

Muscle. 

The muscle mass consists of a series of elongated 
tubular sacks of yellow connective tissue (elastin) ar- 
ranged in bundles and held together by white connective 
tissue (collagen). Interspersed in the mass are fat glo- 
bules. 

Principal Constituents of Muscle. — Proteins. — The total 
proteins of the muscle mass include serum albumin, 
serum globulin, haemoglobin, elastin, collagen, and es- 
pecially paramyosinogen and myosinogen. These latter 
yield myosin on clotting, as shown below : 
paramyosinogen myosinogen 



\ 



\ / 

myosin 

(clot) 



soluble myosin 



HOUSEHOIvD CHEMISTRY I57 

The clotting action takes place at death. The globulin- 
like myosin is in turn gradually softened by acids set free 
by bacterial action (putrefaction) during "hanging." 

Carbohydrate. — Glycogen and glucose are generally 
present in muscle. They furnish energy for muscle con- 
traction, yielding sarcolactic acid as one of the products 
of fatigue. Fresh muscle usually contains glycogen, but 
on standing this is rapidly changed to bacterial lactic acid. 

Extractives. — These are certain nitrogenous non-pro- 
tein bodies, principally creatin and creatinin. They give 
flavor to muscle, and being readily soluble, are found in 
meat extracts and soups. 

Mineral Salts. — Principally potassium phosphate, also 
chlorides and other compounds of Ca, Fe, Na and Mg, 
including a trace of sulphates. 

EXFEEIMENTS ON MUSCLE. 

Cut off the exterior of a piece of lean meat, test the interior 
with litmus paper and note the reaction. Then cut the meat in 
small pieces, pass through a meat chopper and grind the result- 
ing mass in a mortar with clean, dry sand. Take one-half of 
the ground mass and extract in a beaker of cold water, stirring 
every few minutes. Allow the extraction to proceed for J^ hour. 
Finally filter off a part of the watery extract and test separate 
portions as follows: 

1. Biuret 

2. Heat over water. At what point does coagulation begin? 

3. Add crystals of ammonium sulphate to saturation; filter, 
and test precipitate and filtrate with biuret. 

4. Determine whether glycogen is present as follows: Boil 
with a few drops of hydrochloric acid, neutralize, test with 
Fehling's. 

Heat the remainder of the water extract to coagulate the 
protein and filter. To the filtrate add a few drops of HNOs 



158 HOUSEHOI.D CHEMISTRY 

and burn to ash. Cool, take up with water, and if cloudy, filter. 
Divide into five parts and test for chlorides, sulphates, phos- 
phates, calcium and iron. 

Take the second portion of the ground meat, wash it free from 
blood, and extract it with three or four times its bulk of 10 
per cent, sodium chloride, allowing it to stand 24 to 48 hours. 
Finally filter off the protein solution and test portions as follows ; 

1. Try reaction with litmus. 

2. Pour a few drops into a large excess of water. Note milky 
precipitate of myosin. 

3. Heat to coagulating point ; what is it ? Is the litmus reaction 
the same after heating? 

4. Saturate with salt, shaking vigorously. What effect on the 
myosin? Filter. Dissolve precipitate in 10 per cent. NaCl and 
make biuret test on solution. 

From the composition of muscle and the tests made 

deduce the effect on meat of washing, placing in dilute 

salt solution, corning, soup making, and roasting. 

Beef Extracts. 
Composition. — The food value of these extracts is 
slight, and their function is to serve as stimulants or 
appetizers, and flavoring material. Commercial extracts 
contain little if any protein material, since such proteins 
as may be extracted are coagulated by heat and removed 
by filtration. Home-made extracts and clear soups lose 
food value by clarifying. No fats or carbohydrates are 
found in the average market extract; the principal in- 
gredients are extractives and the mineral salts of muscle. 

TESTS ON HOME-MADE AND COMMEECIAL 
EXTRACTS. 

Make meat extract by steeping lean meat in cold salt water, 
gradually heating to a boil and finally under slight pressure. 
Pour off the liquid, cool, remove the fat, dissolve some of the 



house:hoi.d chemistry 



159 



jelly in warm water and compare with Liebig's and other meat 
extracts made on the commercial scale, by the following tests : 

1. Biuret. 

2. Glycogen test (Iodine). 

3. Creatinin (Weyl's Test). — ^Add a few drops of a 5 per cent, 
solution of sodium nitroprusside, freshly prepared, and cautiously 
38° Baume NaOH. A ruby red changing to straw color shows 
creatinin. 

4. Examine the solid extract under the microscope and note 
the cubical crystals of salt and knife-rest forms of creatinin. 

5. Clarify beef extract with white of egg, filter and test filtrate 
for protein with biuret. Compare with test on beef extract 
before clarifying. 

Milk. 

This term usually refers to cow's milk in market form. 

Analyses show that the composition of milk varies with 

different breeds of cows, the principal variation being in 

the fat content. Approximate averages are as follows.* 





Per cent. 


Per cent. 


Wfltfr 


87.2 
12.8 

3.6 

3-3 
4.9 
0.7 


87.0 

13.0 

4.0 

3.3 

5-0 
0.7 


Xotal solid*; •• 


fat 


Drotpin .••• -» 


carbohydrate 

asli .... 





In most states, the amount of fat in milk offered for 
sale is regulated by law. The New York State Standard 
requires at least 3 per cent. fat. 

The Fats. — The true fats in milk are glycerides of both 

volatile and non- volatile fatty acids. Of the former, 

* For detailed composition of milk, see Sherman's I^ood 
Products. 



l6o HOUSEHOIvD CHEJMISTRY 

butyrin is the most important, forming 5 to 7 per cent, 
of the fat content. When hydrolyzed, its free butyric 
acid gives a taste and odor to rancid butter. The prin- 
cipal fats of the non- volatile acids are palmitin in large 
amount, stearin, and olein. In freshly drawn milk tiny 
globules of fat are held in suspension by the mixed pro- 
teins present, but on standing the emulsion breaks, and 
the cream separates more or less completely. However, 
it is not until the emulsifying power of the protein is de- 
stroyed by the action of lactic acid developed in souring, 
that the fat particles run together and are combined in 
the form of butter by churning. 

Proteins. — The protein constituents of milk are prin- 
cipally caseinogen, with small amounts of albumin, glo- 
bulin, and fibrinogen. Caseinogen is strongly acid in 
character, is insoluble in water, but is held in solution 
as a calcium-caseinogenate by the lime phosphates in the 
milk. 

Carbohydrate. — Lactose is the main form of carbohy- 
drate material. In amount it shows less variation than 
any other ingredient except mineral salts. 

Ash Constituents. — The principal ash constituents are 
in the form of lime phosphates, found either combined 
with protein or other organic material, such as lecithin, or 
free as mineral salts. Combined citric acid is present in 
small amount, also chlorides and other salts of Na, K 
and Mg. Iron and sulphur are found. 

Other Constituents. — Urea, creatinin, lecithin, choles- 
terol and hypoxanthine are present in varying amounts; 



HOUSE^HOIvD CHEMISTRY l6l 

also a color substance, carbohydrate- and fat-splitting 
enzymes, an oxydase, a reductase, and a catalase. 

Fresh milk has an amphoteric reaction to litmus, due 
to the fact that it has two classes of phosphates in solu- 
tion. Its specific gravity varies from 1.029 to 1.035. 

Effect of Heating. — Under the conditions usually em- 
ployed for pasteurization (145° F. for i hour) few 
if any chemical changes are produced in milk — the object 
being to destroy certain pathogenic bacteria. Boiling 
milk produces both physical and chemical changes, some 
of which are the alteration in the physical state of the 
fat globules, a tendency to precipitation of the lime salts, 
the destruction of most organisms, and the appearance of 
total solids in the skin which forms after boiling. This 
formation is not, as sometimes explained, coagulated pro- 
tein material, but is due to the concentration of total 
solids as the water evaporates. 

Souring of Milk. — By the activities of lactic acid 
bacteria lactose is decomposed into lactic acid: 
C,,H,,0,„ H,0 «- 4C3HA. 

Other fermentation products may also be formed, such 
as acetic, propionic or butyric acid, and some alcohol, 
e. g.: 

4C3H,0, ^ 2C,H30, + 4CO, + 4H,. 

lactic acid butyric acid 

When the lactic acid reaches approximately 0.5 per 
cent., caseinogen begins to be precipitated; the extreme 
amount of lactic acid developed is generally about 0.9 
per cent. The action of acids on caseinogen has been 
described under Curdling (p. 146) but the changes taking 



l62 HOUS]eHOI.D CHEMISTRY 

place in this case may possibly be represented by the 
expression : 

(lactic acid) 

Ca-caseinogenate «►-* caseinogen 

(soluble) (insoluble) 

-}- acid Ca -phosphate. 
When baking soda is used with sour milk the acid 
caseinogen combines with the alkaline carbonate, form- 
ing sodium caseinogenate, carbon dioxide and water. 

Action of Rennin. — The clotting action of rennin has 
been referred to under Clotting (p. 146). Conditions for 
the best action of the enzyme are brought out in experi- 
ments on p. 165. 

Fermentation with Yeast. — Milk does not readily un- 
dergo fermentation with ordinary yeast unless some food 
for the yeast is added. For kephir or koumiss a special 
yeast ferment is used, which changes the lactose into 
alcohol, lactic acid, and various other acid fermentation 

products. 

TESTS ON MILK. 
Physical — i. Cream Gauge. — Fill to mark with freshly mixed 
milk. Allow the tube and contents to rest quietly for half an 
hour and read off percentage of top milk from graduated scale. 

2. Lactometer. — Fill a tall jar with freshly mixed milk, tem- 
perature 60° F. Immerse the instrument and when it comes to 
rest read off the percentage of purity on the scale. On the New 
York Board of Health lactometer the zero mark records a 
specific gravity of i.ooo and the 100 mark a specific gravity of 
1.029. In similar manner, determine the purity of skim milk. 
Finally, add water and redetermine the purity; how can you ex- 
plain the result? 

3. Pioscope Test. — Depends on opacity. Place a drop or two 
of freshly mixed milk in the center of the hard rubber disc. 



house:hoi.d chemistry 163 

Cover carefully with the glass plate and compare with the 
standard scale of colors. 

4. Lactoscope Test. — Use Feser's lactoscope. Fill the pipette 
with milk, allow it to run into the cylinder. Cautiously add 
water, shaking after each addition, until the marks on the cloudy 
glass rod are just visible through the liquid. Read off and 
record the percentage of fat at the level of the Hquid. 

5. Microscope Test — Examine a drop of milk under the micro- 
scope; add a drop of 10 per cent, caustic soda and re-examine. 
What is the result? 

Chemical Tests — i. Using fresh milk, what is the reaction with 
delicate litmus paper? 

2. Bahcock Test {Determination of Fat). — This test depends 
on the decomposition of the organic constituents, with the excep- 
tion of the fats, which are at the same time set free in the liquid 
state and may be measured. 

Fill the milk pipette (17.6 cc.) with freshly mixed milk, dis- 
charging the contents into the Babcock bottle, add an equal 
volume of oil of vitriol (specific gravity 1.8). Mix by revolving 
the bottle gently in a small arc, back and forth, until the residue 
disappears and the mass is brown in color. Make tests up in 
duplicate and whirl them for 5 minutes in the centrifuge over 
hot water. Stop the machine, add enough warm water to bring 
liquid level half way up the graduated neck of bottle. Replace 
them in centrifuge and whirl 3 minutes, allowing machine to run 
down. Take out bottle and read per cent, of clear yellow fat 
floating on the water. 

3. Separation and Identification of Caseinogen. — Dilute 10 cc. 
of fresh raw milk with water up to about 100 cc, add slowly 
the least quantity (6-8 cc.) of 2 per cent, acetic acid required to 
precipitate the caseinogen, warming meanwhile to 60°, filter 
through moist fluted paper and reserve the clear filtrate for 
test B. Operate with the residue as follows: 

A. Residue of Caseinogen. Wash several times with the same 
amount of hot 95 per cent, alcohol, evaporate the alcohol extract 
over hot water, notice the appearance of the oily substance 



164 HOUSEHOIvD CHEJMISTRY 

remaining, and make a fat test upon it. Remove excess of liquid 
from the caseinogen residue by pressing between dry filter paper, 
and spread out to dry. Dissolve a portion in about 25 cc. of 
warm 5 per cent, salt solution, slightly acidified with acetic acid. 
Stand in hot water for some minutes and filter. Add a few 
drops of the clear filtrate to a saturated solution of salt, adding 
dry salt if necessary. What are the solubilities of caseinogen 
in salt solutions? Make nitric acid and biuret tests on portions 
of the dissolved caseinogen. Add another considerable portion 
of the clear filtrate to ammonium oxalate, made strongly alka- 
line with NH4OH. Heat and observe white crystalline precipi- 
tate of calcium oxalate. Fuse the remaining portion of dried 
caseinogen with sodium nitrate in a porcelain crucible, cool, and 
extract the contents of the crucible with diluted HNO3 (i : 5). 
Filter, and add a few drops of the clear liquid to (NH4)2Mo04 
solution. Warm and observe yellow crystalline precipitate, indi- 
cating presence of phosphoric acid. 

B. Divide the whey filtrate (reserved) into three equal por- 
tions. 

1. Heat in boiling water and observe the clouding (lactal- 
bumin). Filter, test precipitate for protein, and filtrate for lac- 
tose with Fehling's reagent. 

2. Add potassium ferrocyanide and excess of acetic acid. 
Observe the precipitate of lactalbumin. 

3. Heat in boiling water, filter off lactalbumin, boil the filtrate 
and observe the precipitate, principally insoluble calcium citrate. 
Reserve filtrate. 

Note. — H milk has been thoroughly pasteurized, it will not 
respond to the tests for lactalbumin. 

C. Evaporate the filtrate, from last test, to dryness; ignite in 
the presence of a few drops of HNO3, cool, dilute with water 
and test for chlorides, sulphates and phosphates. 

Analysis of Milk — Measure 5 cc. of milk with a pipette, trans- 
fer it to a weighed shallow porcelain dish and weigh again. 
Difference is weight of milk. Place over hot water (kept just 
below the boiling-point) to evaporate water present in milk. 



HOUSEHOI.D CHEJMISTRY 165 

Cool and weigh; loss is water, residue is total solids. Total 
solids should be 12-13 P^r cent. To extract fat, add about 10 cc. 
of ether to contents of dish, heat over warm water i or 2 min- 
utes, decant solution into a second weighed dish. Repeat the 
ether treatment three times. When dry, weigh original dish: 
the loss is fat. Evaporate ether from second dish, weigh; the 
gain is fat and should check the loss. 

To extract lactose and soluble salts, treat contents of dish 
with warm water. Allow it to stand for several minutes, decant 
the liquid; repeat the operation three times. Dry the dish and 
weigh; loss is lactose and half the mineral salts found in milk. 

Ignite the contents of dish to a gray ash; protein matter will 
burn off. Cool and weigh; the loss is protein, residue is insol- 
uble salts. Assuming that insoluble salts are one-half of the 
total salts, double the figure obtained. To determine amount of 
lactose, substract one-half of total salts from the figure obtained 
on lactose and soluble salts. The difference is the amount of 
lactose. 

Determination of Lactose — Into a glass stoppered cylinder, put 
100 cc. milk and 2 cc. Millon's reagent. Mix thoroughly and 
pour into a beaker placed over hot water. Allow the mixture to 
stand until all protein matter has precipitated, filter off the clear 
whey through moist fluted paper. Make it alkaline with dry 
sodium carbonate, adding a little at a time until pink litmus paper 
turns blue. If cloudy filter again. Pour into a burette and deal 
with it as with sugar. Calculate that 0.068 gram will reduce 
ID cc. Fehling's reagent. 

Effect of Rennet — In the following experiments with rennet, 
make the tests comparative by using the same amount of milk 
and rennet solution throughout, e. g., 10 drops of liquid rennet 
to 30 cc. of milk in each case. 

I. Heat milk to the boiling-point, boil gently for 5 minutes, 
replacing any liquid lost during evaporation by hot distilled 
water, cool to 40° and add rennet ; note the character and amount 
of clot. 



l66 HOUSEHOLD CHEMISTRY 

2. Boil milk 15-20 minutes, keeping the liquid up to bulk as 
before; cool to 40", add rennet; note character and amount o£ 
clot. 

3. To the sample of milk, add 1-2 cc. of ammonium dxalate 
solution (precipitant for lime), boil for 2-3 minutes, cool to 40" 
and add rennet; note character and amount of clot, if any. 
Finally add 5-10 cc. of 5 per cent, calcium chloride solution, 
warm to 40° and note the result. 

4. Add I cc. of 0.2 per cent. HCl to the milk and test with 
rennet at 40°. Does a clot form? Repeat, using i cc. of 10 
per cent. NaaCOs. What is the effect of alkali on rennet action? 

5. Note the effect of rennet on separate portions of milk 
heated to 30°, 40", 50°, 80°. Tabulate the results of the above 
tests. 

Butter-Fats — Half fill two small flasks (50 cc), one with pure 
and the other with skim milk. Add to each half a volume of 
ether and a few drops of caustic soda, cork and rotate well. 
Uncork and place in a beaker of warm water and allow them to 
remain quiet. In a few minutes, note the layer of oil and ether 
floating on the surface. Remove some of the ether layer from 
each with a pipette and evaporate at a low heat. Note the 
differences in amount of the butter residue. 

Souring — i. Place some milk in a wide-mouthed bottle, allow 
it to stand in a warm place for some days or until sour. Finally 
filter off the curd and test the filtrate for lactose and for acidity 
by titrating with lo/N alkali, calculating to lactic acid. What 
weight of bicarbonate of soda would neutralize the amount of 
acid found? 

2. Measure standard cupfuls of slightly sour, moderately sour, 
and very sour milk. Weigh the amount of baking soda required 
to fill a standard teaspoon and add the soda in small amounts 
to the milk sample, mixing thoroughly after each addition, and 
testing with litmus paper. Determine the weight of soda re- 
quired to neutralize the acidity in each of the three samples of 
milk, and express the amount in fractional parts of a teaspoon. 



HOUSEHOI.D CHEMISTRY 167 

Condensed or Evaporated Milks should be diluted with distilled 
water to the original bulk and treated as normal milks. The 
index of condensation may be estimated by observing the rela- 
tive amount of dilution necessary. 

Preserved milks commonly contain cane sugar. Dilute a 
sample to the original bulk, precipitate the caseinogen with dilute 
acetic acid; filter and exactly neutralize the filtrate with sodium 
carbonate and test for sucrose with cobalt chloride and caustic 
soda. 

Formalin in Milk. — Add l drop of ferric chloride solution to 
50 cc. of concentrated H2SO4. Pour 5 cc. of the mixture down 
the side of a test tube containing 20 cc. of the milk under test. 
If formalin is present, a violet band will shortly appear at the 
contact point of the two liquids. 

Analysis of Ice Cream — For Gelatin.— Dilute 50 parts of ice 
cream with 25 parts of water and bring to the boiling point, to 
dissolve any thickener other than gelatin that may be present 
and not in complete solution. To 10 cc. of the product add an 
equal amount of acid nitrate of mercury solution^ and about 
20 cc. of cold water. Shake vigorously, allow to stand 5 min- 
utes, then filter. If much gelatin is present the filtrate will be 
opalescent and cannot be obtained clear. To a portion of the 
filtrate add an equal volume of a saturated solution of picric 
acid. A yellow precipitate will indicate gelatin in any consid- 
erable amount; smaller amounts are shown by a cloudiness. In 
the absence of gelatin the filtrate obtained will remain quite 
clear. 

For Fat — Make estimation as soon as possible after sample 
has melted. Weigh 9 grams of the sample in a Babcock cream 
bottle. Add 30 cc. of a mixture of equal parts by volume of 
concentrated HCl and 80 per cent. CH3COOH. Heat on a water 
bath until well darkened, but short of charring. Whirl in a 
Babcock centrifuge and read the percentage of fat directly. If 
the cream is charred, add ether after the whirling, draw off the 
layer containing the fat into another Babcock bottle, evaporate 

^ Jour. Amer. Chem. Soc, 1907. 



l68 HOUSEHOLD CHEMISTRY 

the ether, fill the bottle with water, and again read percentage 
of fat after whirling. 

Character of Patty Matter. — For observing the char- 
acter of the fat, 30-40 cc. of the cream layer are placed 
in a Babcock cream bottle, i cc. of strong mercuric 
nitrate solution and 20 cc. of petroleum ether are added, 
and after whirling, the ethereal layer is separated, washed 
with water, and the ether evaporated. 

Cheese. 

A product prepared from the caseinogen of milk with 
or without the fat. The milk is clotted with rennet, sepa- 
rated from the whey, ground, salted, pressed into shape 
and cured. The curing operation consists in subjecting 
the cheese mass to the action of certain bacteria and 
moulds, which form acids, hydrolyze the proteins and 
develop flavor and odor. 

Cottage cheese is merely finely divided caseinogen pre- 
cipitated by the lactic acid of the souring process aided 
by the heating and undergoes no further change. 

Cheeses are usually made from cow's milk but may be 
produced from goat's or ewe's milk or mixtures of all 
of them.^ 

EXPERIMENTS ON CHEESE. 

Take a sample of well-cured cheese, grind some of it in warm 
5 per cent. NaCl solution, filter and reserve the residue. 
Divide the filtrate into four parts and test as follows : 
I. For acidity or alkalinity with litmus paper and N/io acid 
or alkali. 

*For further information, see Vult6 and Vanderbilt, Food 
Industries, and Wing, Milk and Milk Products. 



HOUSEHOI.D CHEMISTRY 169 

2. For state of protein matter, by biuret test. 

3. For soluble mineral matter, i. e., sulphates, etc. 

4. For ammonia and sulphides. 

Extract the residue several times with the same portion of hot 
neutral alcohol, cool, and test the extract with litmus paper for 
fatty acids. When cold, observe the cloudy precipitate of esters. 
Separate by filtration and test for free fatty acid and fats. 

Divide the extracted residue into two parts and test as follows : 

1. For insoluble protein. 

2. Burn to white ash and test for insoluble mineral matter — 
phosphates, lime, etc. 

During the incineration, hold pieces of moistened red litmus 
and lead acetate papers in the fumes and record the results. 

Cheeses are frequently preserved in wrappings saturated with 
borax or boracic acid solution. To determine this, steep some 
of the paper wrapping in warm water, filter if necessary, acidify 
with HCl and dip pieces of turmeric paper in the liquid. Dry 
these at 212° F.; a pink color indicates borates. 



CHAPTER XI. 



BAKING POWDERS. 

It is frequently necessary to develop carbon dioxide 
for leavening purposes more rapidly than by the agency 
of yeast. For this purpose the purely chemical method 
by the acid decomposition of carbonates or bicarbonates 
is most available. 

Undoubtedly the time-honored custom of using salera- 
tus (bicarbonate of potash) and sour milk (lactic acid) 
furnished the original idea on which the modern mix- 
tures were built up. This idea still survives to some ex- 
tent in modern practice, but is open to at least two 
strong objections. First, bicarbonate of potash is no 
longer a commercial article but is replaced by the cheaper 
and stronger bicarbonate of soda ; still no change is made 
in the proportions used. Second, it is very difficult to 
estimate the amount of lactic acid in sour milk by simple 
means with any accuracy. In fact the quantity is usually 
largely over-estimated. When milk shows decided in- 
dications of the sour stage only 0.4 per cent, of lactic 
acid are usually found. It must be remembered that any 
excess of the bicarbonate used is changed into alkaline 
normal carbonate by the heat of baking. 

For the above stated reasons it can easily be seen that 
accurately compounded mixtures (leaving neither alka- 
line nor acid residues), retaining their qualities for some 
time in the dry state, but ready to develop gas on addi- 
tion of water, have a decided advantage. In order to 
preserve these mixtures in a dry state, it has been found 



HOUS^HOI^D CHEMISTRY I7I 

advisable to add to them such agents as raw starch and 
pulverized lactose, which are perfectly harmless. Such 
additions do not usually exceed 25 per cent, of the whole 
mass. When used for this purpose the compounds are 
known as ''fillers." 

Modern baking powders may be classed as tartrate, 
phosphate, and alum phosphate. All contain bicarbonate 
of soda, while the acting acid ingredient varies, as 
follows : 

Tartrate — Cream of tartar, KHC4H40e, and some- 
times a small amount of free tartaric acid, HoC^H^Oe- 

Phosphate — Soluble phosphate of lime, CaH4(P04)2, 
and sodium dihydrogen phosphate, NaH2P04. Alum 
phosphate, in which alum is now rarely used, being re- 
placed by basic sodium aluminium sulphate or S. A. S., 
Na2S04, Al2(S04)3Al203. 

The following reactions show the changes taking place 
in using these mixtures : 

For tartrates : 

KHC.HPe + NaHCOg + 3H,0— > 

188 84 54 

KNaC,H,0,, 4H2O + CO,. 

282 44 

For phosphates : 

CaH,(P0j2 + sNaHCOg -f- loH.O — 

234 168 180 

CaHPO^ -I- Na^HPO,, i2H,0 + 2CO,. 

136 358 88 

or 

NaH,PO,+ NaHCO^+iiH^O— >Na,HPO„ i2H,0+C02. 

120 84 198 358 44 

12 



17^ HOUSEHOI.D CHEMISTRY 

For alum phosphate : 

Na,SO, A1,(S0J, Al,03 + CaH,(POJ, + 

586 234 

4NaHC03 + 28H,0 —- 

336 504 

MO, + A1,(P0J, + CaSO,, 2H,0 + 

102 244 172 

3Na,S0„ loH.O + 4CO,. 

966 176 

It is sigfnificant that the sodium phosphate and tartrate 
powders leave no insoluble residue except starch, while 
the others leave nearly one-third of their weight in in- 
soluble mineral material besides the starch. The calcium 
phosphate powders yield acid soluble phosphate of lime, 
of doubtful utility, and the alum powders, aluminium ox- 
ide, aluminium phosphate and calcium sulphate. 

The table of comparison on p. 173 is taken from Vulte 
and Vanderbilt's Pood Industries. 

- An efficient baking powder can be made at home at a 
low cost by combining the following ingredients : 
Yz pound cream of tartar. 
y^ pound baking soda. 
J4 pound cornstarch. 
For maximum efficiency these suggestions should be ob- 
served : Dry the cornstarch before combining ; mix and 
sift the ingredients thoroughly; either make up small 
quantities or pack in small tightly closed receptacles. 

Ammonium carbonate is sometimes used as a baking 
powder, since it yields carbon dioxide when heated : 
(NHJ,C03 — NH3 + CO, + H,0. 

It will be seen that all the products are volatile, no 
residue being left unless an excess of the powder is used. 



HOUSEHOLD CHEMISTRY 



173 





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174 HOUSEHOI.D CHEMISTRY 

In that case an unpleasant taste is noticed in the product. 
The amount of powder required is only about one-tenth 
as much as of other powders. 

EXPERIMENTS. 

Tartrates — Mixtures of cream of tartar and bicarbonate of 
soda with starch or lactose filler. Treat a small portion of the 
powder with water and after the effervescence has ceased test 
a portion of the liquid for starch with iodine solution and for 
lactose with Fehling's solution, boil the remainder of the liquid, 
cool, filter through fluted paper, and test with litmus paper. 

1. Place a few drops of the clear liquid on a slide and allow 
it to evaporate spontaneously. Examine the cleft rectangular 
crystals of Rochelle salt. 

2. Fenton's Test. — Test another portion of the solution by add- 
ing I drop of fresh cold dilute solution of ferrous sulphate, 
I or 2 drops of peroxide of hydrogen and immediately a large 
excess of 38° Baume caustrc soda — a violet color appears, due to 
tartrates. Evaporate the balance of the solution in a porcelain 
dish, char and gently ignite the residue. Note the odor while 
carbonizing; what does it suggest? Cool, add water and test 
with litmus paper; why is it alkaline? 

Neutral tartrates will respond to the silver mirror test. 

Tartrate powders may contain a small amount of bicarbonate 
of ammonia. To test for this, heat a portion of the powder in 
a test tube with caustic soda solution ; observe the odor ; or hold 
a strip of moistened red litmus paper over the mouth of the 
tube. 

Phospliate Powders — Calcium hydrogen phosphate or sodium 
dihydrogen phosphate, bicarbonate of soda and starch filler. 

Treat 2 grams (^ teaspoonful) with water and gentle heat 
until the gas is expelled. Be careful not to gelatinize the starch. 
Filter and test filtrate for calcium, sodium and phosphates. Test 
a portion of the residue for starch and treat the remainder with 
cold dilute HCl, testing the resulting Hquid for calcium, phos- 



HOUSEHOI.D CHI:MISTRY 175 

phates and aluminium. From the results obtained decide to 
what class of phosphates your sample belongs. 

Note. — Probably the best method for the determination of 
aluminium compounds is to add a few cc. of a solution of the 
powder to tincture of logwood diluted with 2 or 3 volumes of 
water, finally adding an equal volume of ammonium carbonate. 
In the presence of alum the liquid is colored lavender or dark 
blue. 

Carbon Dioxide Determination by the Scheibler Apparatus 

Weigh out SCO milligrams of the baking powder, place in the 
glass-stoppered bottle belonging to the apparatus. Put a small 
quantity of water in the gutta percha tube (two-thirds full). 
The columns of water in the apparatus will be at the same level 
when the pressure inside of the apparatus is the same as the 
atmospheric pressure, and this should be the condition when 
the experiment is started. The gutta percha tube is placed inside 
the bottle containing the 500 milligrams of baking powder and 
the apparatus is then connected up. Be sure the relief valve is 
open when the apparatus is put together and closed immediately 
afterwards. Incline the generating bottle to allow the water to 
come in contact with the powder. Observe the evolution of gas. 
Note the height of the water column. Grasp the generating 
bottle by the neck and shake vigorously until no more gas is 
evolved. Immediately afterwards balance the water columns by 
allowing some water to escape into the overflow flask. Read 
the figure nearest the level of the water. This reading indicates 
the per cent, of gas liberated by the addition of water to the 
baking powder, or in other words, the leavening power of the 
baking powder. This reading should be in the neighborhood of 
10, indicating 100 per cent, efficiency, in a fresh tartrate powder. 



CHAPTER XII. 



TEA, COFFEE, CHOCOLATE AND COCOA. 

Tea consists of the cured, dried and rolled leaves of a 
variety of plants known as the Thea. According to the 
age of the leaf gathered, there are four well known 
grades. Pekoe the youngest, Souchong next, Congou next 
and Bohea the oldest. All these are found in the grades 
of green or black as the method of curing varies. Green 
teas are not fermented, black teas are fermented, and 
since fermentation tends to reduce the amount of tannin, 
the latter are very generally preferred. 

The principal constituents of tea are the alkaloid 
caffein, tannin, ash, and essential oil. As a rule more 
caffein is found in black teas than in green, and more 
tannin and essential oil in the latter. 

A proper infusion of tea is made by steeping the leaves 
in freshly boiled water (preferably slightly hard) just 
below boiling. Five minutes is sufficient to make the ex- 
tract, when it will contain the maximum of oil, extract 
and caffein and the minimum of tannin. It should now 
be poured off the leaves and used. Boiling or long stand- 
ing increases the amount of tannin in the infusion, while 
it does not materially affect the caffein or extract. 

EXPERIMENTS ON TEA. 

Make an infusion according to rule given in the text, pour off 
the clear liquid, filtering if necessary, and examine the leaves 
with a magnifier. Add a few drops of the clear filtrate to a 
weak starch solution faintly colored with iodine; if tannin is 
present the color will fade. Determine caffein in the balance of 
the extract as follows: Add basic acetate of lead as long as a 



HOUSEHOLD CHEMISTRY 177 

precipitate appears, filter, wash slightly, reject the residue, add 
NaaHPOi solution to the clear filtrate to precipitate excess of 
lead as phosphate, filter and wash. Concentrate the filtrate to 
small bulk (25 cc), cool, transfer to a separatory funnel and add 
5-10 cc. of chloroform. Mix well, and after settling draw off 
the chloroform layer into a weighed porcelain dish and drive off 
the solvent over hot water. Cool and weigh. Caffein crys- 
tallizes in minute colorless needles, possessing a bitter taste. 

After removing the chloroform, evaporate some of the tea 
extract in a clean porcelain dish over hot water and note the 
large amount of residue, also its color and gummy nature. 

Coffee consists of the dried, fermented and roasted 
beans of the Caffea arahica — an evergreen shrub. In 
the roasting process flavor is increased owing to the con- 
version of a carbohydrate constituent to caramel, and the 
development of caffeol, an oil to which much of the 
aroma of coffee is due. 

Coffee and tea contain about the same amount of 
caffein. In addition the chief ingredients of the former 
are caffetannic acid, cellulose, fat, gum, protein, and a 
sugar. 

French coffee usually contains chicory, the kiln dried 
root of the wild endive; the drying operation produces 
caramel at the expense of sugar and hence the water 
extract is dark in color. 

Coffee substitutes are composed of roasted cereals or 
breads with or without the addition of ground roasted 
coffee. Their extracts may not be entirely free from 
caffein and tannin, but in any case will contain less than 
genuine coffee. The bitter taste and dark color are due 
to caramel. 



178 HOUSEjHOIvD CHEMISTRY 

EXPERIMENTS ON COFFEE. 

Grind the roasted beans to a fine powder, throw half a tea- 
spoonful of the powder into a vessel holding cool water, stir 
well, and note whether any color is imparted to the liquid 
(chicory). 

Moisten i tablespoonful of the powder with cold water, add 
I cup of warm water, bring to the boiling-point and boil 2 
minutes. Filter through paper or cotton and reserve the clear 
filtrate for test as follows : 

Decolorize a small portion with bone-black and when cold test 
for starch with iodine. It should be absent;* if present the 
sample contains cereal or bread. 

Test another portion for tannin (see tea). Determine pres- 
ence of caffein (as under tea), using finely ground, well roasted 
material, and taking about double the amount used in the case 
of tea. Chill some of the clear filtrate; should it turn cloudy, 
make further test for dextrin with alcohol. 

Make warm infusions (not boiled) of coffee, chicory, and a 
blend of the two. Add a small quantity of a saturated solution 
•of cupric acetate to each and filter. Greenish yellow color indi- 
cates pure coffee; red brown indicates chicory; yellow brown 
shows a blend of the two. 

Examine thoroughly extracted coffee grounds under the 
microscope. 

Determine quality of the ash. 

Notes on Coffee Making.^ — Experiments made to com- 
pare the quality and composition of coffee extract pre- 
pared from different grades of granulation and by dif- 
ferent methods lead to the f ollov^ing conclusions : 

I. The finer the granulation the stronger the extract. 
The structure of the coffee granule appears to be such 
that fine grinding breaks down minute compartments, 

^ Taken from the Tea and Coffee Trade Journal, Dec, 1913. 



HOUS^HOIvD CHEJMISTRY 1 79 

which yield increased flavor and color to the infusion. 
For example: 

Coffee of medium granulation, sifted through a No. 6 
sieve, gave 25 per cent, efficiency. 

The same coffee, not sifted, 50 per cent, efficiency. 

Pulverized coffee, 100 per cent, efficiency. 

Therefore, one part of the last will be equal to four 
parts of the first or two of the second. 

2. Fresh granulation is essential. Coffee rapidly de- 
preciates in flavor. 

3. Boiling water is twice as efficient in making the ex- 
tract as water under boiling, e. g., at about 150° F. 

4. The principal extraction of value takes place the 
instant the water boils. If boiling is continued the coffee 
changes color and becomes muddy, because the coarse 
fibrous shell is broken down and yields undesirable ele- 
ments to the infusion. Medium granulation is necessary 
in making a clear boiled coffee. 

5. The use of o^gg in clarifying is not recommended, as 
it does not improve the flavor. It is better to strain off 
the liquor. 

The methods of making introduced in the tests were: 

Boiling. — Boiling water poured on coffee and the in- 
fusion allowed to boil for a few minutes. 

Steeping. — Coffee placed in cold water, brought to a 
boil, and immediately strained off. 

Percolating. — In a coffee percolator. 

Filtration. — Boiling water was made to drip slowly and 
steadily through pulverized coffee in a muslin bag. 



i8o 



HOUSEHOIvD CHEMISTRY 



Scalding. — Coffee was added to actively boiling water, 
vigorously stirred for 30 seconds and the infusion filtered 
immediately. 

The composition of the infusions was found to be as 
follows : 





Per cent, 
extract 


Cafifein 

Grains per 

cup 


CafiFetannic 

acid 
Grains per 

cup 


1. Boiling (Med. Gran.) . 

2. Boiling (Pulv.) 

3. Steeping (Med. ) 

4. Steeping (Pulv. ) 

5. Percolating (3 min. ) • . 

6. Percolating (5 min. ) • . 

7. Filtration (Pulv.) 

8. Scalding (Med.) 

9. Scalding ( Pulv. ) 


2.63 
2.76 
2.42 
2.58 
-1.85 
1.86 

1.51 
1.99 
2.50 


2.58 

0.58 

1.75 
2.86 
2.91 
2.22 

2.35 
2.92 


2.35 
2.41 
2.31 
2.35 
2.21 

2.90 
0.29 
1. 81 
2.31 



' From the above, it will be seen that: 

1. Boiling yields the greatest amount of extract, and 
a relatively high amount of caffein and caffetannic acid. 

2. Steeping yields a lower amount of caffein than (i), 
but about as much caffetannic acid. With medium gran- 
ulation, the least amount of caffein is given. 

3. Filtration gives less extract and less acid. 

4. Scalding is intermediate between filtration and boil- 
ing. 

5. Percolating gives a low extract but high acid and 
high caffein. The reason is that the water in a perco- 
lator does not boil over the coffee, but passes over by 
force of condensation, at a temperature seldom above 
150° F. Hence its power of extraction is low, but its 



hous£;hoi.d chemistry 



i8i 



acid and caffein content will be relatively high, as these 
bodies are soluble in cold water. Caffetannic acid is a 
hindrance to digestion. 

A second series of tests showed the following: 





Extract 


Caffein 

Grains per 

cup 


Caffetannic 

acid 
Grains per 

cup 


Boiled TMed "4 


2.60 
2.30 

1.85 
1.86 
1.03 


2.47 
0.80 
2.86 
2.91 
1.47 


2.44 
2.40 
2.21 
2.90 
0.19 


Steeoed ( Med "1 


Percolated (Fine) (3min.) 
Percolated (Fine) (smin.) 
Filtered (Pulv.) (>^Quan.) 



The conclusion reached in the article quoted is that on 
the whole the filtration method is the best to employ, since 
it uses the coffee in the most efficient form and water 
at its most efficient temperature; the flavor of the in- 
fusion is superior; it is almost tannin free, and contains 
on an average about 15^ grains of caffein per cup. 

Chocolate and Cocoa. — These products are made from 
the fermented and dried seeds of the fruit of the Theo- 
broma cacao, which resembles the cucumber. After dry- 
ing and husking, the seeds yield two halves called "nibs." 

The nibs are ground to a fine powder under hot rolls, 
which melt the large quantity of fat (cocoa butter) 
present and produce a liquid mass. If this is allowed to 
run into shallow molds and cooled, the product is called 
chocolate or bitter chocolate. Sugar and vanilla extract 
are often added to the liquid before cooling, producing 
sweet or edible chocolate. 



l82 HOUSEHOI^D CHKMISTRY 

If the fluid mass of ground nibs is pressed to remove 
fat and the remainder is cast in molds and afterward 
ground, the product is called soluble cocoa. Alkali in 
small amount is frequently used in the effort to make the 
cocoa more soluble, but this is a fallacy. 

The principal alkaloid in the cocoa bean is theobromine. 
Caffein is present in small amount. 

Cheap grades of cocoa contain considerable quantities 
of starch and ground cocoa shells. 

EXPERIMENTS ON CHOCOLATE AND COCOA. 

Boil some of the finely ground mass with water, filter while 
hot and reserve both filtrate and residue for test. 

Tests on Filtrate. — For starch, dextrin, sugar, protein matter 
and soaps. 

Tests on Residue. — Dry and extract fatty matter with gasoline. 
Examine extracted residue under the microscope for fiber. 
Determine quality and amount of ash. 



CHAPTER XIII. 



FER]VIENTS AND PRESERVATIVES. 

The organisms which cause the most common changes 
in our food materials are generally known as yeasts, 
lactic acid and vinegar ferments. Their spores are 
present in all house dust. These organisms are distin- 
guished by the fact that they operate in presence of air, 
under widely varying temperature conditions, and give 
off no disagreeable odors, while their products are non- 
poisonous. It is true that putrefactive bacteria play 
some part in the preparation of our food, notably in 
meats and cheeses, but great care must be observed that 
the process is kept under strict control and allowed to 
proceed only to a limited extent. The activities of these 
various organisms are due to enzymes secreted by their 
cells. 

Yeast Fermentation. — This type of fermentation is 
typically alcoholic. The food chosen for the growth of 
the yeast organisms is mostly carbohydrate material, 
which is decomposed by enzyme action to alcohol and 
carbon dioxide as the principal products. The by-prod- 
ucts are extremely numerous, and include succinic acid, 
glycerol, and traces of esters, aldehydes and complex 
alcohols. The expression CJI^fi^ -^ 2C3H5OH -f 2CO2 
is therefore merely general for yeast action. 

In ordinary yeast the enzymes acting on carbohydrate 
material are maltase, invertase, and zymase. There is 
evidence that phosphates, such as are present in yeast 



184 house:hoi.d chemistry 

cells, are necessary to fermentative changes, as added 
phosphates greatly stimulate fermentation and enter into 
combination with monosaccharid material as a hexose- 
phosphate. 

Due to the specific action of the enzymes present, 
starch and lactose are not acted upon directly by ordinary 
yeast; maltose is changed by maltase to glucose; cane 
sugar is hydrolyzed by invertase, and zymase completes 
the alcoholic fermentation of the monosaccharid prod- 
ucts. Different yeasts have different fermenting action, 
e. g., S. fragilis, found in kefir, has a lactose enzyme. 

Yeasts in general have their optimum activity be- 
tween 68° and 90° F. ; the maximum growth tempera- 
ture for many varieties is about 105° F. In the moist 
condition coagulation takes place at lower temperatures 
than in the dry. Yeasts are killed more or less quickly 
from 111° to 140° F., with moist heat. Sterilization 
with dry heat necessitates long continued high temper- 
atures, or intermittent sterilization. For pasteurization, 
it is well to maintain for some time the lower tempera- 
ture employed, to insure uniform heating of the mass. 
Yeasts are not easily destroyed by cold unless exposed 
to very low temperature for long periods. 

The rate of fermentation increases with concentration 
of the sugar up to a certain limit, then decreases with 
further concentration. When 15 per cent, of alcohol has 
been formed the action ceases, even though the mass 
contains unchanged carbohydrate. 

Lactic Acid Fermentation. — The organisms capable of 



HOUSEHOLD CHEMISTRY 185 

producing this form of fermentation are numerous, and 
operate on various forms of carbohydrate material. 
They have been found in milk, beer, distiller's mash, 
sauer kraut, and other substances. The forms most 
commonly occurring in milk are the Streptococcus 
lacticus, and a similar organism, Bacterium lactis acidi, 
which hydrolyze lactose, and convert the resulting glu- 
cose almost entirely into lactic acid: CgH^g^^g «•-► 
2C3H6O3, with no gas formation. Another organism 
well known for its value in preparing sour milk is B. bul- 
garicum. It hydrolyzes lactose and ferments about 92 
per cent, of both products — galactose and glucose — to 
lactic acid so that the total amount formed is much 
greater than with the organisms described above. These 
ferments are not easily destroyed by cold but do not act 
below 50° F. and continue their work up to 130° F., be- 
ing most active at 110° F. Conditions for sterilization 
and pasteurization are similar to yeasts. 

These organisms represent the true lactic fermentation, 
in which the by-products are almost negligible. A modi- 
fied lactic fermentation is produced by groups of in- 
testinal origin. The products of these are lactic and 
other acids, alcohol and gases — ^lactic acid forming less 
than one-half of the total. 

Salt-rising bread^ and sour dough bread are prepared 
by a method of spontaneous fermentation. The organ- 
isms producing fermentation probably vary, but in some 
instances are those which develop lactic acid and gas 

^See Buchanan: Household Bacteriology^ and The Baker's 
Review^ August, 191 1, to March, 191 2. 



i86 housi:hoi.d chemistry 

from sugar. When corn meal has been used in the fer- 
menting batter, it is probable that the gas mixture (hy- 
drogen and carbon dioxide) is produced by the Bacillus 
coli. A dried form of ferment is now sold for this pur- 
pose. 

Acetic Acid rermentation. — The production of acetic 
acid from alcohol is a type of bacterial action well 
known in everyday experience. The souring of wines 
and the production of vinegar are illustrations of the 
activities of this organism. The ferment, commonly 
known as "mother of vinegar," carries oxygen from the 
air to the alcohol, the oxidation resulting in acetic acid : 

CHgCH.OH + O2 »*-> CH3COOH + H^O 
It acts on all weak alcoholic liquids of 10 per cent, and 
under. The temperature conditions are much the same 
as for lactic acid (50°-! 10° F.). Fermentation ceases 
when 5 per cent, of acid has been produced. Conditions 
for sterilization and pasteurization are similar to yeasts. 

Butyric Acid Fermentation. — Important fermentative 
changes producing butyric acid are brought about by the 
action of many bacteria. Two types of these organisms 
are recognized: 

(i) The non-motile butyric acid bacillus, found in 
milk and in the soil. It is an anaerobic form which fer- 
ments sugars, starch, and under some conditions lactic 
acid, the products being butyric acid, lactic acid, hydro- 
gen, and carbon dioxide. It liquefies gelatin. 

(2) The motile butyric acid bacillus, found in soil, 
water, and cheese. It is anaerobic, does not liquefy gel- 



HOUSEHOI.D CHEJMISTRY 187 

atin, and has a chemical action on carbohydrates similar 
to the non-motile form. 

Other forms are known, of a pathogenic order, which 
act upon both carbohydrates and proteins. 

EXPERIMENTS. 
I. Fermentation of Carbohydrate by Yeast Dissolve a con- 
siderable quantity — about 150 grams — of commercial glucose or 
of molasses in i or 2 liters of water in a good sized distilling 
flask. Dissolve one-fourth of a yeast cake, add to the solution, 
warm to 25° and keep in a warm place until fermentation ceases. 
Distil over a water-bath, noting the temperature at which the 
distillate passes over, and test the latter for alcohol by burning 
a portion and by the iodoform reaction. 

Yeast — Temperature Experiments. — Prepare four 6-inch test 
tubes with perforated corks, bearing tubes bent in the form of 
the inverted letter J. Fill three of the tubes with a mixture, 
prepared from one-half a yeast cake, one-half tablespoonful of 
molasses and a cup of water. Fill the fourth with the same 
preparation filtered through absorbent cotton. Allow tubes Nos. 
I and 4 to stand, while No. 2 is subjected to a temperature of 
32° F. (produced by a mixture of pulverized ice and salt) for 
15 minutes. No. 3 is boiled for 2 or 3 minutes. Now place the 
four pieces of apparatus so that the delivery tube of each 
reaches to the bottom of a test tube containing about 2 inches 
of clear limewater, and allow them to stand for at least 2 hours 
in a warm place (90° F.). At the end of this time examine 
each tube of limewater, first for a precipitate, and second with 
litmus paper. Finally examine the liquid in the fermentation 
tubes, noting its odor and general properties. 

For the action of yeast on soluble carbohydrates, see p. 98. 

Lactic Acid — To about 6 ounces of pasteurized milk contained 

in a small flask, add i tablespoonful of the liquid obtained by 

dissolving one lactobacilline (Metchnikoff) tablet in half a cup 

of tepid water. Mix well and keep at 100" F. for 36 hours. 

13 



l88 HOUSEHOIvD CHEMISTRY 

Carefully observe all changes taking place and compare with the 
well known buttermilk. 

Acetous Fermentation — ^Make a weak solution of alcohol in 
water (5 parts of alcohol to 20 parts of water) and test with 
litmus paper; if acid, neutralize with a weak solution of sodium 
carbonate and test a small portion with potassium iodide and 
potassium hydroxide; heat — the odor of iodoform shows the 
presence of alcohol. 

Divide the balance of the solution into two equal parts, pour 
one into a shallow dish and place the other in a well-corked 
bottle. After the solutions have stood for a week, test with 
litmus paper, and also by adding alcohol and warming gently. 
Note the peculiar odor of ethyl acetate — odor of hard cider — in 
the first case but not in the latter. Explain. 

Expose a small quantity of beer to the atmosphere for several 
days; subsequently examine for acidity with test paper and for 
acetic acid with alcohol. From the results of these experiments 
explain why bottled weak alcoholic beverages keep sweet. 

Butyric Fermentation — Neutralize some sour milk with chalk, 
,add a little decaying cheese, and allow to stand for some hours. 
The butyric ferment in the cheese acts on the lactic acid in a 
neutral medium, as follows: 

2CH3CHOHCOOH —^ CsHtCOOH + 2CO2 + 2H2 

Note the growing acidity and odor of the milk. 

All foods are subject to the attack of bacteria and in 
consequence their value is very generally seriously im- 
paired. Methods for prevention of these changes have 
been used from the earliest times and are known as 
preservation. 

At least tv^o general types of process are in common 
use, vi2., physical and chemical. To the first class be- 
long such methods as drying, cooling, and canning. These 
processes are applicable to all kinds of foods, possess 
liigh efficiency and make very slight changes in flavor. 



HOUSEHOI^D CHEMISTRY 189 

appearance and composition. Unfortunately, food ma- 
terials preserved in any of these ways will change very 
rapidly with a slight variation of physical conditions, 
hence the effects are not permanent. The second class 
involves such change of chemical conditions that no mat- 
ter what physical changes may occur, decomposition can- 
not take place. The results are permanent but are ac- 
complished at the expense of flavor, appearance, etc. 

So general has the use of chemical preservatives be- 
come that a brief discussion of the subject seems nec- 
essary. The best known and, as generally conceded 
harmless, are: alcohol, vinegar, sugar, and salt (NaCl). 
With the exception of vinegar (acids generally being 
inimical to bacteria) the action seems to depend on mak- 
ing the protein matter present insoluble; hence we find 
the quantity of the preservatives important. Well known 
operations are as follows: 

Alcohol — 50 per cent. "Brandying." 

Salt — dry or supersaturated solution "Pickle." 

Sugar — syrup — solutions of 25 per cent, or more. 

Less well known methods accomplish similar results 
by using very small, in some cases minute proportions, 
of other chemical agents ; but the actual chemical opera- 
tion can only be surmised in most cases. Included in this 
list are: borates, fluorides, sulphites, peroxides, formal- 
dehyde, benzoates, salicylates and creosote. It may be as 
well to observe that the use of spices, for instance in 
mince meat, is certainly parallel with benzoates and 
salicylates. 

Boric acid, borax and borates are eflicient in small 



190 HOUSEHOI.D CHEMISTRY 

quantities — as low as i per cent. Their use in preserving 
meats is not permitted at present in the United States. 

Sulphites can not now be used for giving cut meat a 
red appearance. 

It has not been proved that sodium benzoate is danger- 
ous in the amounts used for food preservation, and it is 
allowed under the Food and Drugs Act, provided the 
label states the fact. Salicylic acid is not allowed. 

Wood tar creosote is very efficient as a non-poisonous 
preserver of meat. 

EXPERIMENTS. 

Alcohol and vinegar are first separated by distillation and then 
identified by well known methods. Sugar and salt may also be 
determined by diluting, filtering and testing the clear filtrate. 

Borates. — Ash some of the substance, cool, make strong water 
extract, filter if necessary and neutralize with dilute HCl. Dip 
a strip of turmeric paper in this liquid, remove and dry by steam 
heat, (This may be accomplished by wrapping the moist paper 
around the upper part of a test tube partly filled with water 
and boiling gently.) The paper turns pink on the edges. 

Or moisten the ash in the dish with alcohol, add 8 to 10 drops 
of glycerin, mix well with a glass rod and ignite the mass with 
a match or Bunsen burner. Note the yellow flame with a green 
edge, characteristic of borates. 

Fluorides. — Mix the liquid or solid mass with an excess of 
limewater, evaporate to dryness, ignite, cool and make the etch- 
ing test. * 

Sulphites. — If present in quantity, they are distinguished by 
their odor and taste, "sulphur match," especially on warming. 

For small amounts of sulphites, mix with bromine water, boil 
off excess and test for sulphates. Sulphates may be present in 
the original liquid, in which case precipitate by BaCla, and HCl, 
filter and use the clear filtrate as above. 

Formaldehyde. — See page 199. 



HOUSEHOI.D CHEJMISTRY I9I 

Benzoates. — Carefully mix liquid substance with one-tenth of 
its volume of chloroform and a few drops of commercial sul- 
J)huric acid. Avoid violent shaking (mix with a rotary motion). 
Allow the mixture to remain quiet until chloroform layer sep- 
arates. Remove some of this layer with a pipette and evaporate 
it in a clean porcelain dish over hot H2O. Note the flat crystal- 
line plates of benzoic acid, which give off a pungent odor on 
heating. Examine the original mixture in the flask, note any 
violet color between layers of acid liquid and chloroform. This 
indicates salicylic acid. 

Both benzoic and salicylic acids are not present in the same 
liquid. 

TESTS FOR PTTRITY OF CERTAIN FOODS. 

Sanitary Condition of Milk — The presence of a large number 
of bacteria in milk indicates staleness or an insanitary condition. 
The following test will give some indication of its purity: First 
sterilize all utensils used by keeping in boiling water ^ hour. 
Warm i pint of milk to body temperature and add one junket 
tablet which has been dissolved in i tablespoon of cooled boiled 
water. Stir until thoroughly mixed and allow to stand quietly 
until the milk has clotted. Cut the curd in cross-sections with 
a knife and carefully pour off the whey. From time to time, 
draw off the whey as it accumulates. When the curd is com- 
pact, cut it with a knife and observe its condition. If it is firm 
and smooth with but few holes, the milk does not contain an 
abnormal number of bacteria. If the curd has a spongy appear- 
ance, bacteria are present which have produced gas. Place a 
tablespoon of the curd in water ; if it sinks, the milk is compara- 
tively clean; if it floats, the milk is stale or in an insanitary 
condition. 

Formalin In Milk — See page 166. 

Genuine Butter. — See page 140. 

Coal Tar Coloring in Butter, etc. — 1. The custom of coloring 
butter is very largely practiced in the United States. Vegetable 
dyes, such as annatto, have been employed in the past, but coal 



192 HOUSEHOIyD CHEMISTRY 

tar products (anilin dyes) are now quite frequently used. Coal 
tar yellow may be detected by the following experiment : Into 
a weak solution of alcohol, put i teaspoon of butter, a small 
amount of cream of tartar, and bits of white silk or wool. Boil 
the mixture. If coal tar coloring is present, the samples will 
be dyed. 

2. Melt a teaspoonf ul of butter in a test tube at low heat. Add 
an equal volume of Low's reagent (mix 4 parts CH3COOH, 
I part H2SO4) ; shake well, heat nearly to boiling, and set aside 
to separate into layers. The acid layer will be colored red if 
azo dyes have been used. Pure butter gives a faint blue tinge. 

Annatto — Place about 100 cc. of milk in a cylinder, make 
alkaline with sodium carbonate solution, insert a long strip of 
heavy white filter paper and allow to stand in a dark place for 
about 12 hours. Withdraw the paper, wash gently in running 
water and observe against a fresh piece of the same kind of 
paper. If annatto is present, the paper will have taken up some 
of the color. Prove by dipping the strip into a solution of 
stannous chloride. It becomes pink. 

' Alnm in Food Products — Make water solution and follow 
method under Baking Powders, page 175. 

Copper Compounds in Canned Goods — As a rule, coloring mat- 
ter is not added to domestic goods. Imported varieties, as green 
peas, having an intense color, usually have copper added in 
small amounts. It may be detected by adding a few drops of 
hydrochloric acid to a portion of the material and dropping in 
a bright steel nail or the blade of a knife. If copper salts are 
present, a reddish color will appear on the steel. 

Purity of Olive Oil — See Halphen's Test, Page 139. 

Purity of Extracts Vanilla. — (a) Vanilla extract shows a 

nearly colorless foam on shaking ; in case vaniUin has been used 
the foam will be colored due to the addition of caramel for the 
purpose of imitating the vanilla color. 

(b) Leach's Test— To 40 cc. of the sample add an equal 
volume of normal lead acetate (dissolve 189.5 grams of 
Pb(C2H302)2, 3H2O in water and make up to i liter). If a 



HOUSEHOI.D CHl^MISTRY I93 

precipitate settles the vanilla is pure ; vanillin gives no precipitate. 

Lemon Extract — Test by adding a few drops of the extract 
to water. The true lemon oil is insoluble in water, and a milky- 
appearance results. Artificial lemon extract gives a clear water 
solution. 

Saccharin — This substance may be added to canned products 
in place of sugar. It is a coal tar product having several hun- 
dred times the sweetening power of cane sugar. To determine 
its presence shake 15 or 20 cc, of the suspected liquid in a flask 
with an equal volume of chloroform. Saccharin is soluble in 
chloroform; while sugar is insoluble. With a medicine dropper 
remove some of the chloroform which has settled to the bottom. 
By gently heating in a porcelain dish, evaporate the chloroform. 
Taste the residue; if sweet, saccharin is present. 

Freshness of Eggs — Candling is one of the methods most 
frequently used. In a darkened room hold an egg between the 
eye and an artificial light, A fresh egg should appear unclouded, 
homogeneous, and almost translucent. If dark spots are found, 
it is stale. A rotten egg appears dark colored. 

Against the larger end of a fresh egg between the shell and 
the lining membrane, a small air cell should be distinctly visible. 
In an egg which is not perfectly fresh, this space is filled with 
the egg substance, unless the egg has been stored with the large 
end up. 

Salt solution test: As the density of an egg decreases by the 
evaporation of moisture, its freshness may be approximately esti- 
mated by placing it in brine. Prepare the salt solution by dis- 
solving 2 ounces of salt to i pint of water. Immerse the egg 
in the solution. A perfectly fresh egg will sink; if several days 
old, it will swim just immersed in the liquid; if stale, it will 
float on the surface. 

Shake an egg, holding it near the ear. The contents of a fresh 
egg should not move. If a slight movement can be detected, it 
is somewhat stale; if it rattles, the egg is spoiled. 

Open the egg and observe the odor and taste. If there is a 



194 HOUSEHOI^D CHEMISTRY 

tendency for the white and yolk to run together, the egg is not 
fresh, or the hen has been improperly fed. 

Coflfee — See Experiments, page 178. 

Gelatin in Ice Cream Page 167. 

Vinegar has been very largely subject to substitution and imi- 
tation. The best varieties on our market are cider, wine, and 
malt vinegar. Substitution may be detected by slowly evapo- 
rating almost to dryness ^ cup of vinegar in a small evaporating 
dish and examining the warm residue. If there is a distinct 
odor of baked apples, it is cider vinegar; of grapes, it is wine; 
and of malt, the product is malt vinegar. Distilled vinegar gives 
a burnt sugar odor; no residue indicates synthetic vinegar. 



CHAPTER XIV. 



DISINFECTANTS AND DISINFECTION. 

These terms apply to the destruction of bacterial or- 
ganisms and their spores. Some confusion of ideas 
exists with regard to the respective action of disinfec- 
tants and antiseptics. A disinfectant is a germicide; an 
antiseptic retards or prevents bacterial activity. A de- 
odorant simply absorbs or covers up noxious vapors. 

Physical Methods of Disinfection or Antisepsis. — Sun- 
light. — The direct rays of the sun are powerful enemies 
of bacteria, the bacillus of tuberculosis, for example, 
being killed by sunlight. 

Dry Air. — Dry air arrests the activities of bacteria by 
removing conditions of moisture favorable for their 
growth, and oxidizes the products of their action through 
the work of aerobic organisms in the air. 

Cold Storage. — This is an efficient temporary method 
of inhibiting bacterial activity. It should be understood 
that freezing and cold storage are not the same. In 
freezing, the expansion of the ice crystals disrupts the 
structure of food and leaves it open to attack. Food 
that has been frozen should therefore be consumed as 
soon as possible after thawing. 

Pasteurisation. — Bacteria likely to be present in im- 
pure milk are killed by a temperature of 60° to 70° main- 
tained for 20 minutes to i hour, according to the tem- 
perature employed. The organisms which escape are 
comparatively harmless in eifect. 



196 HOUS^HOIvD CHEMISTRY 

Boiling. — Typhoid and tuberculosis bacteria are killed 
by boiling for i minute. Drinking water and milk are 
likely to be sterilized by this treatment. To destroy the 
spores of some other forms of pathogenic bacteria, boil- 
ing must be repeated on two or three successive days. 

Some Common Antiseptics. — Salt, sugar, spices, vinegar, 
and creosote have considerable efficiency as antiseptics. 
The power of salt, sugar, and vinegar to inhibit the action 
of bacteria depends upon the strength of their solutions. 

Chemical Means of Disinfection. — Mercuric chloride, 
or corrosive sublimate, is one of the most powerful of 
germicides. Its use is limited, partly because it is a 
violent poison, partly by its tendency to form a precipitate 
with many inorganic and organic substances, such as 
hard water, alkalies, protein bodies, etc. A solution of 
one part of mercuric chloride in one thousand parts of 
water is commonly employed. 

Carbolic Acid. — This is frequently used in very dilute 
solution as an antiseptic wash, as a powerful antiseptic in 
a strength of i to 400, or as a germicide in stronger 
solution, such as 5 per cent. 

Formaldehyde. — Formaldehyde is antiseptic in weak 
solution, and germicidal in the 40 per cent, solution called 
formalin. For room disinfection the formaldehyde gas 
is used, produced by lamps which pass methyl alcohol 
vapor and air over hot oxidized copper, or by heating 
paraform. This substance is a solid polymer of form- 
aldehyde, which gives off the gas when heated. Form- 
aldehyde is also produced from formalin heated under 



HOUSEHOI^D CHEMISTRY I97 

pressure, or treated with dehydrating agents to cause 
an evolution of the gas. 

Sulphur Dioxide. — This is a powerful disinfectant, but 
has the disadvantage of being also a strong bleaching 
agent, and therefore cannot be used in the presence of 
colors. The gas is produced by burning sulphur, com- 
monly in the form of a sulphur candle. It is irrespirable, 
and has produced fatal results when in the proportion of 
about 5 per cent, in air. To do away with the necessity 
of using fire to produce sulphur dioxide, its solution in 
water as sulphurous acid is frequently used. This acid 
is unstable, and when exposed to the air gives off sulphur 
dioxide and water. 

Copper Sulphate. — This compound ranks next to mer- 
curic chloride in antiseptic power. It is soluble in four 
parts of water, and in i per cent, solution is disinfectant ; 
in weak solution, e. g., o.i per cent., it is antiseptic in 
most cases. 

Zinc Chloride is strongly antiseptic and disinfectant, 
and is useful for drains. A solution of i to 5 per cent, 
is employed for ordinary antiseptic purposes. Zinc oxide 
is much used in the preparation of cold creams and oint- 
ments, and is a mild antiseptic. 

Hydrogen Peroxide is a powerful oxidizing agent, as it 
decomposes into water and nascent oxygen. It has a 
bleaching action on fabrics, but is not as destructive to 
the material as are Javelle water or bleaching powder. 
As a disinfectant it is comparatively slow in its action, 
but the evolution of oxygen is hastened by the addition 
of a small amount of an alkali, such as borax, to the 



198 HOUSEHOI^D CHEMISTRY 

solution. In dilute solution hydrogen peroxide is non- 
poisonous. 

''Chloride of Lime*' or Bleaching Powder. — So-called 
chloride of lime, used for disinfecting purposes, is cal- 
cium hypochlorite, Ca(C10)2. A similar compound, 
sodium hypochlorite, is known as Javelle water. The 
action of both depends upon the available chlorine they 
contain, which when set free unites with water to form 
eventually hydrochloric acid and nascent oxygen. The 
carbon dioxide of the air, or other acid present, is neces- 
sary to bring around the reaction. Using acid : 

Ca(C10X -f 2HCI— > CaCl, + 2HCIO 

2HCI -h 2HCIO — 2H,0 -f 2CI, 

CI, + H,0 — 2HCI + O. 

Both hypochlorites are strong bleaching agents and are 
especially destructive to wool and silk fabrics. Cotton 
and linen materials are not seriously affected, but should 
be rinsed free from bleaching powder or Javelle water if 
these are used for disinfecting clothes. The latter solu- 
tion is better for this purpose. Bleaching powder is 
often used for drains in about 10 per cent, solution. 

Washing Soda. — In the strength used in the laundry, 
washing soda has little antiseptic effect, but is efficient 
in about 2 per cent, hot solution as a disinfectant for 
washing floors and walks, milk cans, etc. 

Soap has considerable antiseptic power. So-called dis- 
infectant soaps have little advantage over ordinary pure 
soaps unless the proportion of disinfecting ingredient 
is high, and it is in readily soluble form. 



HOUSEHOI.D CHEMISTRY I99 

Tests for Disinfectants. 

On account of the small quantities of material usually 
employed, many of the ordinary analytical tests fail to 
give conclusive results. Hence the following methods 
are suggested, as being more reliable in the majority of 
cases. 

Mercuric Chloride. (Found usually in one or two parts, or 
less, per thousand.) — To 50 cc. of the solution in a large test 
tube add a few cc. of a mixture of equal parts of weak potassium 
iodide and ammonium chloride solutions (each i per cent.) 
and immediately 2 or 3 drops of caustic soda. A yellow color or 
brown precipitate developing after a few minutes' standing indi- 
cates mercury. It will be noticed that this test is a reversal of 
Nessler's test. 

Carbolic Acid — To the clear liquid add bromine water in slight 
excess and immerse in hot water until all odor of bromine is 
dissipated. A white bulky precipitate of bromphenol indicates 
carbolic acid. 

Formaldehyde is best indicated by the violet band appearing 
as a zone when the liquid containing the aldehyde is carefully 
poured upon a large volume (10 cc.) of commercial concentrated 
sulphuric acid (oil of vitriol) held in a test tube. The color is 
due to ferric salt always present in the crude form of the acid. 

Sulphur Dioxide or Sulphites — Indicated by warming the acidi- 
fied (HCl) solution — an odor of burning sulphur is apparent. 
Or by adding barium chloride to the acidified solution, boiling, 
and filtering off the first precipitate (a precaution necessary due 
to the presence of sulphates), finally adding a few drops of 
nitric acid to the clear filtrate and boiling again until oxides of 
nitrogen and chlorine are expelled. A white precipitate of 
barium sulphate remains, insoluble in hydrochloric acid. 

Copper Sulphate. — Indicated by a deep blue color on adding 
ammonium hydroxide in excess, or by a reddish brown precipi- 
tate in potassium ferrocyanide solution acidified with acetic acid. 



200 HOUSEHOIvD CHEMISTRY 

Ferrous Sulphate — Indicated by a deep blue precipitate in 
contact with dilute potassium f erricyanide solution, which decom- 
poses on addition of sodium hydroxide and leaves a brownish 
residue. 

Permanganates. (Alkaline potassium or sodium). — Impart a 
pinkish color to the liquid even in dilute solution. The color 
is quickly discharged on adding a mixture of dilute sulphuric 
and oxalic acids and warming, or by a few drops of fresh 
ferrous sulphate solution acidified with dilute sulphuric acid. 

Hydrogen Peroxide — Indicated by the deep blue shade im- 
parted to ether when in contact with an acidified mixture of po- 
tassium dichromate and peroxide. 

Bleaching Powder ("Chloride of Lime") — Sets free the halo- 
gen from potassium or sodium iodides. If chloroform is added 
the iodine dissolves in it with a violet color. In the presence of 
starch, the iodide of starch (blue color) is formed. 



CHAPTER XV. 



CLEANSING AGENTS. 

The number of compounds put on the market for 
household use in cleansing and allied operations is con- 
stantly increasing, and in many cases extravagant claims 
are made with regard to the efficacy of the preparations. 
The public is led to believe that each one represents the 
discovery of a new and powerful detergent. As a matter 
of fact, analyses of these preparations show that they 
are merely variations in combination of a few well known 
cleansing agents. A general classification of cleansers 
and similar compounds reduces them to a few principal 
groups : 

1. Soaps and soap powders. 

2. Scouring powders. 

3. Metal polishes. 

4. Bleaches and stain removers. 

5. Grease solvents. 

6. Bluings. 

Soaps and Soap Powders. — As shown in Chapter IX, 
soaps are a product of the saponification of a fat by an 
alkali. Sodium or potassium hydroxide is commonly 
used. The type formation of the soap is as follows : 

(HOH) 

(i) Fat »-> fatty acid + glycerol. 
(2) Fatty acid + alkali »-► soap. 
It will be seen that glycerol is a by-product. It is 
recovered in the commercial method of soapmaking, a 



202 H0USE:H0I.D CHEMISTRY 

process which gives the market its chief supply of this 
commodity. 

The Cleansing Action of soap is both physical and 
chemical. Its solution in water acts as an emulsifying 
agent, loosening and removing dirt particles. Chemically, 
soaps are salts of a strong base and a weak acid, and as 
such dissociate in water with some hydrolysis, e. g. : 

C„H,5C00Na -f HOH — - C.^Hg^COOH + NaOH. 

The alkali set free may form additional soaps with free 
fatty acids present in the greasy impurities of the article 
to be cleansed. 

Soap powders contain dry pulverized soap, together 
with an excess of sodium carbonate in the hydrated form. 
They may or may not contain insoluble mineral matter — 
clay, sand, etc. — and trifling amounts of borax. 

Manufacture of Soap. — Two classes of water-soluble 
soaps are recognized — hard, or soda, and soft, or potash 
soaps. In the former the harder fats and non-drying 
oils are used as a rule; for the latter vegetable drying 
oils and marine animal oils are utilizable. In the manu- 
facture of hard soaps two methods — the cold process or 
boiling — may be employed. The hot process is the usual 
commercial method, as the soap produced is more apt 
to be uniform in appearance and quality, and glycerol 
can be recovered as a by-product. The cold process gives 
a simple and quick method for household use, and if 
operated with intelligence gives a good neutral soap, 
which contains the glycerol. 



HOUSKHOIvD CHEMISTRY 203 

Boiled Soap. — The saponification process is divided 
into at least four stages, although a number of interme- 
diate stages called "washes" are frequently introduced to 
remove impurities. 

The four changes are known as : 

Stock change. 

Rosin change — where no rosin is used this change 

is replaced with a wash. 
Strength change. 
Finish. 

Stock Change. — The required amount of mixed tallow 
and grease or oil are melted together in large iron kettles 
or tanks by the aid of steam coils, the lye is added and 
the whole mass boiled until it is saponified ; at this stage 
the mass of boiling soap has a peculiar smooth appear- 
ance called "closed." Pickle is now added, until the 
contents of the kettle separate into small broken grains; 
this stage is called "open or grained." Heat is turned 
off and the kettle allowed to cool; when cold there will 
be two layers, the upper one of soap, floating on the salt 
lye — this latter is called "spent lye" and should be almost 
neutral. From it glycerin and salt may be extracted. 
The spent lye is then drawn off from the bottom of the 
kettle, leaving the soap for the next operation. If no 
rosin is to be used the "wash change" takes place at this 
point; this consists in adding water, boiling to a "close" 
and then salting out and settling as before; the wash 
lye is worked up for salt and glycerin. 

Rosin Change. — Soap from previous operation receives 
14 



204 HOUSE^HOIyD CHEMISTRY 

an addition of fresh, strong lye, is heated to boiling and 
the rosin in lumps thrown into the kettle; only just 
enough lye to saponify the rosin is used; the amount of 
rosin varies but usually equals the weight of the tallow 
and grease. Boiling is continued until rosin is saponified, 
and then pickle is added to grain; the kettle stands to 
cool; the rosin fat soap rises as before and the rosin lye 
is drawn off and worked for salt and traces of glycerin. 

Strength Change. — The rosin fat soap is now boiled 
with fresh strong lye until saponification is complete. 
It is always found that small amounts of fat and rosin 
escape saponification in the earlier stages unless these are 
unduly prolonged. The kettle is cooled and the soap 
which has been grained or open condition throughout 
this operation (due to strong lye) rises; when cold the 
strong lye is drawn off and used to start the saponifica- 
tion in the stock change. This lye is often mixed with 
that coming from the strength change. 

Finish. — The thoroughly saponified grained soap still 
contains strong lye and many impurities; and this is 
removed by melting and adding water carefully until the 
soap * 'closes," or loses its grained structure. The kettle 
is allowed to cool very slowly, being kept perfectly quiet 
for at least 48 hours. During this time three layers are 
formed, the upper consisting of pure soap, the interme- 
diate of impure dark soap called "nigre," which may be 
sold as such or bleached in a subsequent operation, and 
a very small amount of strong alkaline lye called the 
nigre lye, which is generally thrown away. 



HOUSKHOLD CHEMISTRY 205 

The finished soap is either run into iron box moulds, 
stirred well, and allowed to cool and set thoroughly, and 
then cut; or is run into a "crutcher" or mixing machine, 
where various additions, such as sal soda, silicate, sa- 
ponified rosin, etc., are made. From this machine the 
mixture is run into frames, cooled and cut. 

Half Boiled Soap. — Much of the ordinary toilet soap is 
made by this process, which is as follows : 

The requisite quantity of fat, tallow, grease, cotton- 
seed or coconut oil is heated gently in a jacketed steam 
kettle, enough very strong lye usually mixed; potash or 
soda is gradually added and stirred vigorously ; the oper- 
ation is complete when the hot soap is clear and will run 
in long strings from the trowel or stirrer. The mixture 
is now ladled into frames and allowed to cool and set. 
When cold it is removed from the frame, cut into strips, 
dried, chipped, milled between stone rollers. In the mill- 
ing operation, coloring matter and perfumery are added, 
although for cheap soaps these additions may be made in 
the kettle after saponification. After milling, the soap 
goes through the "plotter," which forms it into long bars 
and cuts these into convenient lengths for pressing. It 
will be noted that the glycerin remains with the finished 
soap in this process. The best toilet soap is made by the 
full-boiled process. 

Average Analyses. — The average compositions of a 
white laundry soap of good quality and a yellow soap 
containing rosin are given on the next page for compar- 
ison : 



206 



HOUSEHOI^D CHE:MISTRY 



Water 

Combined fat as actual soap. • . . 

Rosin 

Na^COa 

Mineral matter, including NaCl 
Free caustic 



Rosin soap 
per cent. 



30.0 
30.0 
35.0 

3-5 
i.o 

0-5 



lOO.O 



White soap 
per cent. 



15-25 
85-75 



100,0 



Use of Rosin. — Rosin is cheaper than soap grease, and 
is introduced primarily as a filler. It is properly classed 
as an adulterant. By its presence more water can be 
incorporated with the soap, hence rosin soaps soften and 
waste away rapidly. It is not strictly a detergent, ex- 
cept as it aids in making a suds, and its continued use 
has a yellowing effect on white fabrics. Based on the 
amount of actual soap contained in soaps of this class, 
they cost more per pound than a good grade of white 
soap. 

Cold Soaps. — For the production of a neutral soap by 
this process, the correct combining amounts of fat and 
alkali must be determined. The mean saponification 
numbers of the fats and oils commonly used call for a 
proportion of i gram of fat to 0.195 gram of KOH, or 
0.139 gi*am of NaOH, i. c, ratios of 5 : i and 7 : i re- 
spectively. Therefore, in practice, 5 units of fat by 
weight combine with i unit of caustic potash, or 7 units 
with one of caustic soda. This calculation is approxi- 



house:hoi,d chemistry 207 

mated by taking the combining weights of the interacting 
substances : 

Ci.HggCOOH + NaOH — - Ci^Hg^COONa + H,0. 

284 40 

Here 284 units of weight combine with 40, giving a 
ratio of 7: 1. 

In round numbers, for 7 pounds of fat, use i 
pound of caustic soda, dissolved in water to a suitable 
bulk. Crude caustic soda, costing a few cents per pound, 
can usually be obtained. The consistency of the fat 
largely determines the amount of water which may be 
incorporated; a fat liquid at ordinary temperatures will 
take up only about enough to dissolve the alkali, more 
solid fats will hold water in amounts varying from one- 
half the weights of fat to equal weights of the two. 

The process of making cold soap consists in melting 
the fat, stirring in the dissolved caustic soda until a 
homogeneous, creamy mass is obtained, and setting the 
mixture aside in molds to complete the saponification 
and harden. Twenty-four hours usually suffices. Some 
household recipes are appended, made on the basis of 
I pound of fat. To obviate weighing 1/7 of a pound of 
the alkali, it is convenient to dissolve a pound in the right 
amount of water, and measure out the particular quantity 
required. 

Laundry Soap. — 1/7 pound NaOH dissolved in suffi- 
cient water to make 14 fluid ounces (i}i cups). Strength 
17° Baume. 

I pound solid fat melted. 



208 HOUSEHOI.D CHEMISTRY 

Emulsion Soap. — Add to the above before it hardens, 
3 tablespoonfuls each of kerosene and a strong solution 
of washing soda. Stir about 5 minutes longer. Incor- 
porate I pint of water for a soft soap. 

Castile. — 1/7 pound NaOH made up to ^ cup with 
water. (38° Baume.) 
I pound olive oil. 

Coconut Oil. — 1/5 pound (full weight) NaOH made 
up to I cup. 

I pound coconut oil. 

(The exact proportions are 53^^ pounds oil to i pound 
NaOH.) 

By stirring in air with an egg beater, the result will be 
floating soap. 

Palm Oil. — 1/7 pound NaOH made up to 154 cups. 
I pound palm oil. 

Special Varieties — Scouring Soaps. — These are made 
by introducing into the soap while in a creamy condition, 
a large amount of finely pulverized quartz or other min- 
eral matter. 

Transparent Soaps. — Such soaps are made by incor- 
porating the amount of alcohol required to hold the soap 
in a clear solid solution. In some cases the transparency 
is produced by the use of sugar, which must be consid- 
ered an adulterant. 

Liquid soaps are soap solutions containing an excess 
of the solvent. 



HOUSDHOIvD CHEMISTRY 20g 

Soap Analysis. — For detailed methods, see Chapter 
XVI. As a simple means of determining whether a soap 
is superfatted or contains excess alkali, apply the follow- 
ing tests: 

TESTS. 

For Free Fat. — Shake a few shavings of the soap in a corked 
test tube with cold gasoline, filter into a convex glass and 
evaporate the gasoline over warm water. A greasy residue in- 
dicates unsaponified fat. 

For Free Alkali — Shake a few shavings of the soap in a 
corked test tube with warm alcohol (95 per cent.), filter and 
add to the clear liquid a few drops of phenolphthalein ; a red 
color indicates free alkali. Or, drop some of an alcoholic solu- 
tion of phenolphthalein on the freshly cut surface of the soap. 

Scouring Powders. — These are improved forms of the 
old crude mixtures of sand and soap, formerly used ex- 
tensively for rough cleaning. They now consist of clay, 
incorporated for absorbent purposes, and pulverized 
soap, containing abrasive material in a more or less finely 
divided condition. Borax may be present, and at times 
clay is partly or entirely replaced by chalk. The common 
fault with such preparations is that their use is recom- 
mended for general cleaning, but they frequently contain 
sharp abrasive particles which make them injurious to 
fine metal or porcelain surfaces. 

Average analyses of these powders are appended : 

Per cent. 

Water 1—6 

Soap 4 — 14 

Sodium carbonate — 24 

Abrasive material 63 — 93 



2IO house:hoi.d chemistry 

Metal Polishes. — These polishing* agents are on the 
market in liquid, paste, and powder forms, also as polish- 
ing cloths. Their action in removing tarnishes— oxide, 
sulphide or carbonate coatings — depends upon the ab- 
rasive effect of pulverized mineral material, the solvent 
action of chemicals, or both combined. 

The liquid polishes are solutions containing as a rule 
one or more of the following ingredients: oxalic acid, 
muriatic acid, ammonia, benzine or benzene, and potas- 
sium cyanide. These may be combined with pulverized 
mineral matter. 

Oxalic acid is very effective in dissolving metallic 
oxides and carbonates, and is therefore in common use as 
a cleanser for brass and other metals. The acid potas- 
sium oxalates are similarly used. The metal itself is 
liable to be attacked by oxalic acid, which should not be 
used in too strong solution for nickel-plated faucets, etc. 

The cleansing effect of muriatic acid is similar to that 
of oxalic, and can be produced in the household by 
using a mixture of salt and vinegar. 

Ammonia is an excellent cleanser for copper and brass, 
but like all chemical solvents for tarnishes, should be 
removed by washing as soon as the metal is clean. 

Benzine and aromatic benzene are valuable constitu- 
ents of liquid polishes, since they act as general solvents. 

Potassium cyanide is used in the trade, but as it is 
a violent poison its use is unadvisable in the home. 

Pastes. — These contain pulverized mineral material 
made into paste form with soap, and in some cases small 



HOUSEHOIvD CHEMISTRY 211 

amounts of oxalic acid, glycerol, or a hydrocarbon. Their 
action is principally abrasive, and the mineral substances 
they contain are those found in the cleaning powders 
described below. 

Powders. — Efficient polishing powders are whiting, 
clay, rouge, talc, quartz, emery, and silica. 

Whiting is finely pulverized chalk. It costs about lO 
cents per pound, and is useful for cleaning silver, nickel, 
porcelain, and glass. A mixture of whiting with water 
or alcohol is effective for window cleaning. One of the 
scouring preparations on the market is essentially a 
mixture of whiting and soap. 

Clay is of varied character and comes under different 
names — Tripoli, rottenstone, etc. These substances cost 
about 40 cents per pound, and when in finely divided con- 
dition are used for general metal cleaning. Rottenstone 
is frequently mixed with kerosene for this purpose. 

Rouge is preferred by jewelers for polishing gold and 
silver, brass and copper. Jeweler's rouge is finely pul- 
verized red oxide of iron, prepared by a special process, 
and costs about 5 cents per ounce. When mixed with 
water it will adhere to the surface on which it is rubbed. 
Some of the best metal polishes on the market are com- 
binations of rouge, oxalic acid, and a hydrocarbon. 

Talc is pulverized magnesium silicate, and makes a 
good polishing agent without danger of scratching. 

Silica, quartz and emery come in different forms, as 
knife bricTc, scouring soaps, etc., and are especially suited 
to the polishing of steel and iron. 



212 HOUSEHOI.D CHEMISTRY 

Polishing cloths are made usually by impregnating 
soft durable fabrics with rouge, talc, rottenstone or 
whiting. A polishing cloth may be made at home by 
dipping a pile fabric or a piece of chamois into rouge 
mixed with water or alcohol, and drying. Some of these 
cloths have no mineral constituent, but polish by means 
of the fabric itself. 

TESTS FOR CLEANING AGENTS. 

Oxalic Acid or Oxalates. — Make a water solution, filter, add 
Ca(0H)3 to filtrate. White precipitate of calcium oxalate ap- 
pears. 

Benzine or Benzene, — Odor and inflammability. 

Ammonia. — Odor and litmus test. 

Potassium Cyanide. — Treat with fixed alkali, FeS04, FeCU and 
HCl in order given. Prussian blue color. 

Whiting. — Add CHsCOOH. An effervescence indicates a car- 
bonate. Make test for calcium. 

' Rouge. — Treat with boiling HCl (cone). If rouge is present, 
it will dissolve. Make iron test with NH4SCN. 

Clay. — Will remain insoluble when treated with water or acid. 

Bleaches, Grease and Stain Removers.— Many pro- 
prietary compounds are sold for these purposes. On an- 
alysis, the bleaches are generally found to be calcium 
hypochlorite, Javelle water, hydrogen and sodium per- 
oxides, oxalic acid, or potassium permanganate, alone or 
in combination. Some description of the use and effect 
of these compounds is given in Chapter XIV. If the 
kind of bleach required is known, it can be bought 
directly, and at less expense than if purchased under its 
proprietary name. For example, ink eradicators usually 
consist of Javelle water or a solution of bleaching 



HOUSEHOLD CHE:MISTRY 213 

powder, accompanied by an acid — oxalic, muriatic, or 
citric — the two being combined at the time of application. 

The non-inflammable solvents for grease, familiar to 
the public, have for the most part carbon tetrachloride 
as their principal ingredient, with varying combinations 
of benzine or gasoline, benzene, acetone, or chloroform. 
They have a great advantage as to safety over the danger- 
ous gasoline or benzine, often used carelessly in the 
home. These grease solvents will remove fresh paint or 
varnish stains, since they attack the fatty constituent in 
the compound. Turpentine, benzene or amyl acetate also 
soften and dissolve dried paint and varnish. 

Bluings. — The character of the bluing used in the laun- 
dry is of importance to the housewife. The three types 
in common use — solid, liquid, and aniline blues — are 
markedly different in properties. 

Solid blues are now commercially prepared ultramarine 
blues, the former type, indigo blue, being little used at 
present. Ultramarine is found in nature in small quan- 
tities as lapis lazuli; as manufactured, it is a mixture of 
sodium and aluminium silicates, and sodium sulphide. It 
is characterized by insolubility in water, but the suspen- 
sion of its fine particles in the bluing water gives a good 
blue color. Unfortunately, unless care is used, larger 
particles sometimes settle on the clothes, and produce 
blue spots. 

TEST. 

Ultramarine blue is decolorized on addition of HCl or H2SO4. 
Sulphur is precipitated and H2S evolved. 



214 HOUS^HOI^D CHI:MISTRY 

Liquid Blues. — These are principally Prussian blue, 
i.e., Fe4[Fe(Cn)6]3. Prussian blue decomposes in the 
presence of an alkali, such as caustic soda, and gives a 
brown residue of ferric hydroxide. This may happen 
if soap is carried over into the bluing water. In that 
case the ferric hydroxide becomes iron rust on the 
clothes, when the hot iron is applied. 

TEST. 

Warm the sample of liquid bluing with NaOH. A brown 
precipitate appears if the bluing has an iron base. Filter, dis- 
solve residue in hot dilute HCl and make test for ferric com- 
pound, with NH4SCN. 

Aniline Blues. — These are used less in the household 
than in commercial laundries, but can be procured in 
powder form at a laundry supply establishment. They 
are cheaper than other forms of bluings, as i ounce of 
the powder will make a strong solution in a gallon of 
water. Acids are used in most laundries for the best 
development of the color on the clothes. If an acid is 
used, it should be acetic, which is volatile and harmless, 
rather than oxalic, which is destructive to most fabrics. 

TEST. 

Aniline blues slowly lose color in the presence of caustic soda. 



CHAPTER XVI. 



VOLUMETRIC AND GRAVIMETRIC ANALYSIS. 

Nonnal Solutions. — The basis of volumetric analysis is 
the normal solution. A normal solution is one which 
contains the hydrogen equivalent of the substance in 
grams, in i liter of solution. For all monobasic acids 
and alkalies the hydrogen equivalent corresponds with 
the molecular weight of the compounds ; for dibasic sub- 
stances it is one-half of the molecular weight. In sim- 
ilar manner tri- and tetrabasic bodies have hydrogen 
equivalents corresponding to one-third and one-quarter 
of their molecular weight. To find the equivalent of a 
salt, refer back to the acid from which the salt is made. 
For example, NagCOg is the sodium salt of H2CO3, 
therefore it is dibasic, and its normal solution would 
contain one-half its molecular weight, or 53, in grams 
per liter. 

Equal volumes of normal solutions of different sub- 
stances are of equal strength, and equal volumes of nor- 
mal acid and alkali solutions neutralize each other. 

Normal solutions may be made one-tenth or one- 
hundredth of their full strength, either by taking the 
corresponding fractions of their respective equivalents 
or by diluting the full normal solutions proportionately; 
they are known as deci- and centi-normal solutions re- 
spectively. 

To explain the preparation of the normal solutions of 
acid and alkali, one example from each class will suffice. 



2l6 HOUSEHOLD CHEMISTRY 

and as hydrochloric acid and caustic soda have the most 
extensive appHcation, their preparation will be given. 

Preparation of N/HCl. — The molecular weight of HCl 
is 36.5, therefore 36.5 grams per liter are needed, but 
as it is a volatile liquid and cannot be weighed with any 
accuracy, it is usual to calculate the volume of the liquid 
from its specific gravity, and to measure out the result 
in cubic centimeters, allowing a little for loss. Using 

W 
the formula — ^^ V, the calculation is simple and is 

made as follows: divide the equivalent in grams (36.5) 
by the specific gravity of the concentrated acid (1.2); 
this gives 30.4+ as a quotient and is the number of 
cubic centimeters to be used if the acid were 100 per 
cent, strength, but the strongest acid is only 40 per cent., 
hence this quotient must be multiplied by 2,5 (30.4 X 
2.5 ^= 76 cc). It is safe to take 78-80 cc, adding it to 
300 or 400 cc. of distilled water and when cool diluting 
to exactly i liter. 

The solution must now be standardized against a nor- 
mal solution of an alkali which can be made exact. 
Sodium carbonate, the equivalent of which is 53, can be 
obtained of a high degree of purity and may be weighed 
exactly. It is hardly necessary to make up a large quan- 
tity, so that 5.3 grams of pure dry soda are usually 
weighed accurately, dissolved in the least quantity of 
water and the resulting solution diluted to exactly 100 
cc. at or about 60° F. This constitutes the exact normal 
soda, I cc. of which contains 5.3 milligrams of soda. 



HOUS^HOI^D CHEJMISTRY 21J 

Measure lo cc. of the soda very exactly with a pipette or 
burette, run it into a small beaker containing about lOO 
cc. of distilled water and add 2 or 3 drops of methyl 
orange solution. Fill a burette with the acid solution. 
Note the level, and run it, drop by drop, with constant 
stirring, into the soda. Stop when the last drop changes 
the color from yellow to pink which remains even after 
stirring for some moments. Read the burette and note 
the number of cubic centimeters, and fractions used. Say 
the quantity is 9.8 cc, indicating that this quantity con- 
tains as much acid as should exist in 10 cc. ; consequently, 
980 cc. of the liquid should be diluted to i liter. If 
the total amount of acid is less, calculate what bulk it 
should occupy and dilute accordingly. Continue the 
titration until equal volumes of acid and alkali exactly 
neutralize each other. 

The acid keeps well, but should be preserved in tightly 
stoppered glass bottles to prevent evaporation. 

Preparation of N/NaOH. — The caustic soda is deliques- 
cent and absorbs carbon dioxide, so must be weighed 
rapidly and approximately, using rather more than the 
40 grams required, say 50 grams. This is dissolved in 
300 or 400 cc. of water, cooled and diluted to i liter. 
Draw off 10 cc. of the normal acid in a pipette, allow it 
to run into a small beaker containing about 100 cc. of 
distilled water, and add a few drops of phenolphthalein. 
Fill a clean, dry burette with the caustic soda. Note its 
level and run it, drop by drop, with constant stirring, 
into the acid solution until a faint but distinct pink tint 



2l8 HOUSEHOI^D CHEMISTRY 

remains after stirring for some moments. Read off the 
quantity used, say 9.5 cc, showing the solution to be too 
strong and requiring dilution as in the case of the acid. 
After performing this operation the acid and the alkali 
should be correct and i cc. of one will exactly neutralize 
an equal quantity of the other. 

Use of Indicators. — A change in a solution from acidity 
to alkalinity, or the reverse, can be shown by certain 
color substances or indicators, sensitive to the slightest 
excess of acid or alkali.^ The indicators in common use 
in acidimetry and alkalimetry are phenolphthalein and 
methyl orange. The work of an indicator may be illus- 
trated by the action of phenolphthalein, a weak acid 
which undergoes little dissociation in solution. In the 
non-ionized state it is colorless. If, however, its acid 
solution is neutralized by an alkali, a slight excess of the 
alkali forms a salt of phenolphthalein which ionizes with 
a deep red color. A strong base is necessary in order to 
give a sharp reaction. Ammonia, for instance, is too 
weak a base to ionize the weakly acid phenolphthalein in 
dilute solution. Phenolphthalein is used most frequently 
as an indicator for weak acids (excepting carbonic and 
hydrosulphuric) titrated against normal sodium hydrox- 
ide. 

Methyl orange, on the other hand, is red in its molecu- 
lar state, and changes to yellow on dissociation. It is 
a moderately strong acid, and if added to a basic solu- 
tion the salt formed is yellow, but the addition of a 

^ For Theory of Indicators, see Ostwald : Foundations of 
Analytical Chemistry^ and Cairns : Quantitative Analysis. 



HOUSEHOI.D CHEMISTRY 219 

slight excess of a strong acid is sufficient to produce the 
red color of the non-ionized substance. Its reaction 
with weak acids is not sharp, so its use is not advised in 
connection with organic acids. Because of its strongly 
acid nature methyl orange is useful in titrating against 
weak bases. It must always be used in cold solution, 
and in small amounts. 

Congo red and rosolic acid are usually employed in 
the Kjeldahl determination of nitrogen. The former is 
blue in acid solution, red in alkaline. It is dissolved in 
water for use, and only small amounts should be taken. 
Rosolic acid is yellow in the presence of acids; cherry 
red with alkalies. It is dissolved in 50 per cent, alcohol 
for use. 

To test unknown substances, first determine the com- 
pound present by qualitative analysis, and then weigh or 
measure some convenient quantity, dissolve or dilute 
with distilled water, add the indicator and run in the 
acid or the alkali until the neutral point is reached. Ob- 
serve the number of cubic centimeters used, multiply 
each by its value in milligrams of the substance sought, 
and divide the result by the quantity used; multiplying 
this quotient by 100 will yield per cent. 

Value of I cc. of normal soda in each of the following : 

Sodium carbonate 0.053 

Acetic acid 0.060 

Lactic acid 0.090 

Tartaric acid 0.075 

Citric acid 0.064 

Hydrochloric acid 0.0365 

15 



220 house;hoi.d chemistry 

Nitric acid 0.063 

Sulphuric acid 0.049 

Potassium hydroxide 0.056 

Ammonium hydroxide 0.035 

Calcium hydroxide 0.037 

For example, to neutralize 10 cc. of a solution of 
acetic acid of unknown strength, 8 cc. of N/NaOH are 
required. The calculation would be : 

I cc. N/NaOH = 0.06 gram acetic acid. 

8 cc. N/NaOH were used. 

8 X 0.06 gram := 0.48 gram acetic acid in 10 cc. 

100 X (0.48 -r- 10) = 4.8 grams acetic acid in 

100 cc. 
.'. the strength of the acid is 4.8 per cent. 

APPLICATIONS OF VOLUMETRIC ANALYSIS. 
. Analysis of Vinegars — Take the specific gravity of the sample. 
Decolorize a portion (50-100 cc.) by passing it through a bone- 
black filter, rejecting the first funnel full. Take 10 cc. of the 
product, dilute with a convenient bulk of water (about 50 cc), 
add I or 2 drops of phenolphthalein as indicator, and titrate 
against N/NaOH. Calculate as acetic acid, using the specific 
gravity of the vinegar to check the resulting per cent. Example : 

Specific gravity of sample may be 1.014, .:. weight of 10 cc. = 
10.14 grams. 

Amount of acetic acid found in 10 grams may be 0.534 gram. 

• '• 0-534 -^ 10.14 = 5.26, the per cent, of acetic acid in the 
sample. 

To distinguish the source of vinegar, evaporate 10 cc. to dry- 
ness, and note the odor. Cider vinegar will give an odor suggest- 
ing baked apples ; malt vinegar, a malt odor ; distilled vinegar, a 
sharp acid odor. Ignite at a low temperature to Hght-colored 
ash. In the case of genuine cider or wine vinegars the quantity 



HOUSEJHOI.D CHISMISTRY 221 

of ash is comparatively large and the reaction will be alkaline. 
Synthetic vinegar will leave no appreciable residue. 

Test for Free Mineral Acids.^ — Dilute 5 cc. of the vinegar 
with 5 to 10 cc. of water to reduce the acidity to about 2 per 
cent, of acetic acid, and add 4 or 5 drops of a solution of methyl 
violet (i part of Methyl Violet 2B, No. 56, of Bayer Farben- 
fabrik, Elberfeld, in 10,000 parts of water). Mineral acids 
change the blue violet color to a blue green or green. 

Test for Phosphoric Acid. — Burn to ash in the presence of a 
few drops of HNO3 and make the usual test for phosphoric acid. 

Baking Soda. — Test for Purity." — Ordinary baking soda may 
contain some NaaCOa. To determine the percentage of NaHCOs 
in the sample, dissolve i gram of commercial NaHCOs in 100 cc. 
of distilled water, add 2 drops of methyl orange, and titrate 
against N/10H2SO4. Since the freed carbonic acid is too weak 
an acid to produce the red color with methyl orange, the latter 
will give the end point of titration in this case only when the 
N/io H2SO4 has neutralized the total alkalinity (combined as 
mono- and bicarbonate) of the soda. 

Now dissolve another gram of the sample in 250 cc. of cold 
water, add phenolphthalein, and titrate with N/io HaSO*. The 
nose of the burette should dip into the solution, which should 
be well stirred during the titration. No carbonic acid should 
escape from the liquid during the operation. Under suitable 
conditions of dilution and temperature the reaction is: 
2Na2C03 + HjSO^ "-^ 2NaHC03 + Na^SO^. 

Therefore, i cc. of half -normal sulphuric acid equals 0.106 gram 
of NaaCOa present. 

The difference between the amounts of N/io acid used in the 
two titrations is the measure of the bicarbonate of soda in the 
sample. 

Cream of Tartar — Test for Purity. — ^Weigh i gram of cream 
of tartar, add 100 cc. of distilled water, and 2 drops of phenol- 

^ From Sherman's Organic Analysis, 
* Cairns : Quantitative Analysis. 



22.2. HOUSEHOI.D CHEMISTRY 

phthalein. Run in N/NaOH until the pink color comes. (A 
certain amount of the alkali is necessary to the complete solution 
of the cream of tartar.) Now add N/io HCl drop by drop until 
the color just disappears, and subtract the amount used from 
the alkaH in terms of tenth-normal. The difference is the amount 
of NaOH required to neutralize the cream of tartar. Calculate 
the percentage of cream of tartar in the sample. 

Household Ammonia. — Take the specific gravity of the sample, 
and dilute lo cc. with a convenient bulk of distilled water. Add 
2 drops of methyl orange, and titrate against N/HCl Calculate 
percentage strength, using the specific gravity as a factor. 

Analysis of Soap or Soap Powder — In a 3-inch porcelain dish 
place 1-2 teaspoonfuls of clean dry sand and a small glass 
stirring rod; weigh the whole. Add 2-3 grams of the soap 
sample, finely shaved, and enough 95 per cent, alcohol to cover 
the material. Evaporate over a water bath, stirring meanwhile, 
until the alcohol is evaporated. Dry the contents of the dish 
in an air bath at 105° to constant weight. Estimate the loss in 
weight as water. 

Weigh another gram of the sample, finely shaved, and heat for 
2-2y2 hours in an air bath, at 105°. Treat the dried material 
on a hot water bath with successive portions of hot neutral 95 
per cent, alcohol, using about 50 cc. at a time and 400-500 cc. in 
all. Decant each portion of the solution through a balanced 
filter paper, finally washing the last portion through the filter 
with additional alcohol. The combined filtrates contain the dis- 
solved soap ; the residue on the filter paper is carbonates, chlor- 
ides, borates, etc., and insoluble mineral matter. Proceed with 
residue and filtrate as follows: 

I. Residue. — Treat filter paper with boiling distilled water until 
all trace of alkalinity or residue in the last 2 or 3 drops of the 
filtrate has disappeared. Dry the paper in the air bath for about 
an hour and calculate weight of insoluble material remaining on 
it. Examine this under a magnifying lens for the presence of 
glistening particles of pulverized quartz, etc. Make up the water 
extract of the soluble material to bulk (e. g., 500 cc), take 100 cc. 



HOUSSHOI.D CHEMISTRY 223 

and determine total alkalinity by titrating against N/H2SO4. 
Calculate as NasCOs. In another 100 cc. calculate chlorides by 
first exactly neutralizing with dilute HNO3, then titrating with 
N/io AgNOa. Use potassium chromate as indicator. Calculate 
that I drop of N/io AgNOa is equivalent to 0.000293 gram 
sodium chloride. Concentrate a third portion to one-tenth bulk, 
and make a qualitative test for borax as follows : Exactly neu- 
tralize with dilute HCl, immerse a strip of freshly prepared 
turmeric paper in the liquid, and dry at warm water heat. Make 
a second test for borax on another portion, by boiling down 
until all of the watery liquid has disappeared, cooling, adding a 
mixture of equal parts of alcohol and glycerol, and applying a 
flame. If the mixture burns with a yellow flame bordered with 
green, borax is present. 

Evaporate the balance of the solution to dryness, heating 
finally to 110°, take up with a little water and a few drops of 
HCl, and test for sulphates and silicates. 

2. Filtrate. — Heat on a water bath until the odor of alcohol 
has disappeared, keeping the solution up to full amount by addi- 
tions of water. Cool, bring solution up to bulk, and determine 
free alkali (NaOH) by titration against N/H2SO4. Then add 
a known excess of the normal acid (e.g., 5 cc), boil until clear, 
add a weighed quantity (about 5 grams) of white wax, and melt. 
Allow the mixture to stand undisturbed until the wax hardens, 
remove the cake, press it between filter papers to remove all 
moisture, and when dry weigh. The increase in weight is due 
to fatty acids. Titrate the solution against N/NaOH. The 
difference between the 5 cc. N/H2SO4 added at the beginning 
and the result now obtained gives the combined alkali. It 
should amount to about one-seventh the weight of the. fatty acids. 
Take the sum of the weights of combined alkali and fatty acids 
as the measure of the soap present in the sample. 

Report in percentages the findings of water, carbonates, 
chlorides, free and combined alkali, fatty acids, and insoluble 
matter. 

Test for Naphtha Soap — Make a strong water solution of the 



224 HOUSEHOI^D CHEMISTRY 

soap sample in a small flask, acidify slightly with diluted H2SO4, 
and distill the mixture at as low a temperature as possible. If 
any hydrocarbon is present it will pass over and condense with 
the watery vapor. Note the odor. 

For the detection of rosin or rosin oil in soap see the 
Liebermann-S torch Reaction, Sherman's Organic Analy- 
sis. 

Analysis of a Cereal. — The process consists in the de- 
termination of water, ash constituents, protein, fat, and 
carbohydrate. 

1. Water. — Dry 1-2 grams of the powdered cereal to constant 
weight, at not over 105°. Calculate percentage of water, and use 
figures obtained in correcting subsequent determinations of other 
constituents. 

2. Ash Constituents. — Ignite 5 grams of the material in a muffle 
furnace at the lowest possible heat to char the material thor- 
oughly. Cool, and make hot water extract of soluble alkaline 
Salts. A small portion of this liquid should be tested for chlor- 
ides, sulphates, sodium and potassium. 

Separate by filtration and evaporate the liquid. Dry the 
charred residue and ignite to white or light-colored ash. Cool 
and add the water extract and evaporate to dryness. Weigh; 
the result is total ash. Test the ash qualitatively for its con- 
stituents, by the following method : 

Dissolve in dilute HCl with the aid of heat, the residue if 
any should be small in amount and light in color. Any effer- 
vescence observed before heating indicates CO3, confirm with 
lime water Ca(0H)2. Make preliminary tests for iron and am- 
monia on small separate portions of the liquid, the balance of 
which is now divided into three unequal parts: Aj^, B^, CJ4- 
Treatment of A. 

Add y2 a volume of FcaCla and NH4CI and enough NH^OH to 
make the mixture decidedly alkaline, boil until the odor of 
ammonia is faint and filter hot. 



HOUSEHOIvD CHEMISTRY 



225 



Precipitate : 
Fe and Al as 
phosphates 
and hydro- 
oxides. 



Dissolve in the 
least possible 
amount of cold di- 
lute HCl, add a 
slight excess of 
clear NaOH, filter 
and exactly neu- 
tralize the clear fil- 
trate with dilute 
HCl. A white floc- 
culent ppt. of 
Al(OH)3. 



Filtrate: 
Ca, Mg, K and Na as chlo- 
rides. Make decidedly al- 
kaline with NH^OH, add 
(NHJaCjO^ boil and filter. 



Precipitate : 


Filtrate: 


CaCaO^ sol- 


Cool, add 


uble in di- 


more 


lute HCl. 


NH4OH and 




NajHPO^ 




shake well. 




Ppt. 




NH^MgPOi. 



Operation with B. 

Divide into three equal portions. 
Part I. 

Add to this a few drops of silver nitrate ; a white curdy ppt. of 
silver chloride, soluble in ammonium hydroxide. 
Part II. 

Add two drops of hydrochloric acid and a little barium chlor- 
ide, a white crystalline ppt. of barium sulphate insoluble in HCl. 
Part III. 

Add a few drops (not more than 10) to i inch of ammonium 
molybdate in a 6-inch tube. Heat the mixture in boiling water 
about two minutes. A yellow crystalline ppt. ammonium phos- 
phomolybdate. 

C may be used in case of accident. 

Protein, — Weigh 1-2 grams of the sample, place in a Kjeldahl 
flask, add 20 cc. of concentrated sulphuric acid, 10-12 grams of 
potassium sulphate, and 0.5 gram of copper sulphate. Partly 
close the neck of the flask with a small funnel for purposes of 
condensation, and heat under a hood, gently at first and then 
strongly, until the mixture is colorless. It is well to continue 
heating for 15-30 minutes after this stage is reached. The nit- 
rogenous matter in the cereal has been converted into ammonium 
sulphate by the acid of the sulphuric acid. The process now 
consists in liberating ammonia from this by the addition of caus- 



226 HOUSEHOI.D CHEMISTRY 

tic soda, distilling the free ammonia into a known amount of 
sulphuric acid, and calculating the amount of nitrogen present. 

Proceed by cooling the material in the Kjeldahl flask, adding 
about 250 cc. of distilled water, and after the solid matter has 
dissolved, 4 or 5 drops of rosolic acid. Put 100 cc. of N/io 
H2SO4 and a few drops of Congo red in an Erlenmeyer receiv- 
ing flask, and arrange to connect distilling and receiving flasks 
with a water condenser. The delivery tube of the condenser 
should reach below the acid in the receiving flask. Place small 
pieces of zinc and paraffin in the Kjeldahl flask to prevent bump- 
ing, add 80 cc. or more of caustic soda (about 38° Be.) and 
connect up at once. Distill over a low flame at first, later in- 
crease the heat, until about half the contents of the flask have 
passed over. If the color in the receiving flask becomes red, 
showing an excess of ammonia, quickly add a measured addi- 
tional amount of the N/io H2SO4. Titrate the excess of acid in 
the flask against N/io NaOH and calculate that i cc. of N/io 
H2SO4 is the equivalent of 0.0014 gram nitrogen. As the av- 
erage percentage of nitrogen in protein material is approximately 
16, the grams of nitrogen found multiplied by the factor 6.25 
will give the amount of protein in the sample.' 

Fat. — Weigh 1-2 grams of the air-dried, pulverized material, 
place in an extraction thimble, and introduce into a Soxhlet or 
other approved form of extraction apparatus. Extract with a 
pure form of ether into a tared flask. The duration of the 
extraction depends on the character of the material, but 16 to 
24 hours are usually allowed. 

Remove the flask, evaporate the ether, weigh, and calculate 
amount of extract. 

Carbohydrate. — Determine carbohydrate by difference. If the 
cereal has a notable amount of soluble carbohydrate, make a 
water extract, invert and estimate reducing sugar, and determine 
the insoluble carbohydrate by difference. Use the following 
method : 

* For modifications of the Kjeldahl method see Sherman; 
Organic Analysis, 



HOUSEHOLD CHEMISTRY 22/ 

Estimation of Reducing Sugars — Mix 15 cc. o£ Fehling's solu- 
tion A with the same amount of Solution B in an Erlenmeyer 
flask of about 250-300 cc. capacity, add about 50 cc. of freshly 
boiled distilled water, and heat in boiling water for 5 minutes. 
Measure with a pipette 25 cc. of the sugar solution, which should 
be of such a strength as not to contain more than 0.5 gram of 
reducing sugar. Add this to the Fehling's mixture and place 
the flask in boiling water for 15 minutes. Remove, filter at once 
with the aid of moderate suction through a Gooch crucible pre- 
pared with asbestos.^ If the filtrate is not distinctly blue, showing 
that an excess of Fehling's has been used, the operation must 
be repeated with a more dilute solution of the reducing sugar. 
Wash the precipitate of cuprous oxide with boiling distilled 
water until the filtrate is no longer alkaline. The cuprous oxide 
can now be (i) washed with alcohol and then with ether, dried 
in an air bath at 100° for 20 minutes, weighed as cuprous oxide, 
and calculated to its cupric oxide equivalent. The corresponding 
weight of reducing sugar may then be determined by referring 
to Defren's table (see Sherman: Organic Analysis). 

Or (2) the cuprous oxide may be ignited and weighed as cupric 

^To prepare the Gooch crucible for gravimetric determina- 
tion of cuprous oxide, proceed as follows : Boil a good quality 
of asbestos with nitric acid (specific gravity 1.05 to i.io), wash 
with water, boil with 25 per cent, sodium hydroxide, wash, and 
repeat the treatment. Finally stir the washed asbestos with 
water, pour some into a Gooch crucible, and draw it into place 
with moderate suction. When a tight felt about i centimeter 
thick has been laid down, ignite to constant weight and record 
weight of crucible and asbestos. Test by running through it a 
"blank" of hot alkaline Fehling's solution and washing with 
water as in a regular determination. The loss in weight should 
not exceed }4 milligram. If it does, the filter is again treated 
with acid and alkali until it ceases to lose in weight. The cruci- 
ble may be used for successive determinations by dissolving the 
precipitate each time with nitric acid, washing, igniting to con- 
stant weight. 



228 house:hold chemistry 

oxide and a corresponding amount of reducing sugar found 
as before. A third method consists in determining the copper 
by electrolysis (see Allihn's method and table for the determina- 
tion of dextrose). 



CHAPTER XVII. 



REAGENTS. 



Commercial 
forms 



Acids 
HCl.... 



HNO3 

H2SO, 

CH3COOH 



Alkalies 
NH^OH 
NaOH . 
KOH .. 

Salts 



NagCOs 
BaCl, . 
(NHJ.C^O 
Na,HP04 
NH.Cl .. 
(NHjjSO 
NH^SCN 
NaCl.... 
MgSO,.. 
HgCl^... 
Tannin. . 
AgNOs . . 

Co(N03)2 
K,Fe(CN)e 



I<aboratory strength 



Sp.gr. 



1.2 



1.4 

1.84 

1.06 



0.9 



Per 
cent. 



40 

70 

94 
50 

28 



Concentrated 


Sp.gr. 


full strength 


1.2 


Vols. 


Vols. 




H2O 


acid 




I 


I 


1.2 


full strength 


1.84 


full strength 


1.06 


full strength 


_ 


20 per cent. 


1.3 


20 per cent. 


1.23 


dry 


— 


dry 





dry 


— 


dry 


— 




- 


— 



Dilute 



Vols. 
H2O 



Vols, 
acid 



3 I 

7 I 

10 I 

Vols. Vols. 
H2O alk 

I 

10 per cent. 
10 per cent. 

10 per cent. 

10 per cent, 
saturated 
saturated 

10 per cent, 
saturated 
5 per cent, 
saturated 
saturated 
saturated 

20 per cent. 
5 per cent. 

10 per cent. 

10 per cent. 



Sp. gr. 



I.I 



I.I 

I.I 
1.007 



0.945 
1. 14 
I.I 

I.I 



1.2 



Special Reagents. 

Ammonium Molyhdate, (NH4)2Mo04. 

Dissolve 100 grams M0O3 in 200 cc. strong NH4OH 



230 HOUSEHOI.D CHEMISTRY 

and 200 cc. H^O; slowly pour resulting solution in 1,500 
cc. HNO3, specific gravity 1.2. 

Magnesia Mixture. 

I gram MgSO^ or MgCl2, i gram NH.Cl, 4 cc. am- 
monia, 8 cc. water. 

Millon's Reagent. — 100 grams mercury dissolved in 
71.5-72 cc. HNO3 specific gravity 1.4 in the cold, 
when action ceases add twice the volume of cold water. 

Fehling's Reagent. — Solution A — 34.64 grams CuSO^, 
5H2O in 400 cc. of cold water, when dissolved make up 
to 500 cc. 

Solution B — 50 grams NaOH + 180 grams NaKC^ 
H^Oe in 300 cc. of water, when dissolved and cooled 
make up to 500 cc. 

For use mix equal volumes of A and B and add two 
volumes of water. 

Barfoed's Reagent. — 4.0 grams copper acetate, 100 cc. 
water, 2 cc. acetic acid. 

Ny lander's Reagent. — Two grams bismuth sub- 
nitrate, (BiONOg), and 4 grams of Rochelle salt, 
(NaKC4H406), in 100 cc. of 8 per cent. NaOH, specific 
gravity 1.08. 

Nessler's Reagent. — 35 grams of Kl and 13 grams of 
HgCla in 800 cc. H2O. Heat below boiling until dis- 
solved, add immediately a cold saturated solution of 
HgClg, until the red precipitate fails to dissolve after 
stirring. Cool and add 160 grams KOH dissolved in as 
little water as possible, and make up to i liter. After 
standing 24 hours pour off the clear liquid and reserve 
for use. If necessary, add a little more (3-5 cc.) HgClg 



house:hoi,d chi^mistry 231 

to increase the sensitiveness. When properly prepared, 
the solution has a pale yellow color. 

Gries's Reagent for Nitrites. — Dissolve i gram of sul- 
phanilic acid in 300 cc. of acetic acid, specific gravity 
1.04 (30 per cent.). 

Boil 0.2 gram of a-naphthylamine in 400 cc. of dis- 
tilled water, filter through a plug of washed absorbent 
cotton and add 360 cc. of acetic acid (30 per cent.). 

To dilute 50 per cent, acid to 30 per cent., take 3/5 of 
100 or 60 cc. of acid and dilute to 100 cc. 

Basic Acetate of {Sugar of) Lead Solution. — Boil 232 
grams of lead acetate and 132 grams of litharge (PbO) 
in 750 cc. of distilled water for half an hour, cool and 
dilute to I liter. Allow liquid to stand until clear and 
decant. Specific gravity of solution should be about 1.267. 

Alumina Cream for Clarifying Syrups, Etc. — Make a 
saturated solution of powdered alum [KA1( 80^)2] in 
water at 6o°-7o° F. ; set aside a small portion (o.i of the 
whole) and add to the balance ammonium hydroxide, 
carefully with stirring, until the mixture is just alkaline 
to litmus paper. Drop in the reserve liquid until the mass 
is faintly acid. This mixture consists of aluminium hy- 
droxide suspended in ammonium sulphate solution. 

Meta Phosphoric Acid. — Dissolve glacial phosphoric 
acid (HPO3) or phosphoric anhydride, P2O5, in ice and 
water. As the solution rapidly changes to H3PO4 make 
it fresh for each day's work. 

Alcohol. — 95 per cent, is always acid; neutralize with 
dilute alkali before using. Alcohol may readily be recov- 



232 HOUSEHOLD CHEMISTRY 

ered from solutions and wash liquids by distilling over 
hot water at 78°-8o°. 

Ammonium Sulphide. — Mix equal volumes of dis- 
tilled water and strong ammonia (specific gravity 0.9) ; 
divide the resulting solution in equal parts. Pass a cur- 
rent of H^S through one-half the solution until saturated 
and then add the balance of the dilute ammonia. 

Alkaline Pyrogallol. — Dissolve 20 grams of the best 
pyrogallol in 100 cc. of cooled freshly boiled distilled 
water, add 0.5 cc. of concentrated H2SO4. This solution 
keeps well. 

For use take enough of the above and make strongly 
alkaline with 10 per cent. NaOH. Avoid contact with 
air and use immediately. 

Alkaline Potassium Permanganate. — 8 grams of crys- 
tallized potassium permanganate with 200 grams of 
caustic potash or a corresponding amount of caustic 
soda, in i liter of water. 

Acidified Potassium Permanganate. — 0.395 gram po- 
tassium permanganate in i liter of water. Add 10 cc. of 
H2SO4 before using. 

Alcoholic Potash. — 56 grams KOH in i liter 95 per 
cent, alcohol. 

MoliscKs Reagent. — Make a 15-20 per cent, alcoholic 
solution of alpha-naphthol. Use with H2SO4 as directed. 

Schweitzer's Reagent. — Dissolve 5 grams of copper 
sulphate in 100 cc. of boiling water, add caustic soda solu- 
tion until the cupric hydroxide is completely precipitated, 
wash the precipitate well and dissolve in the least quan- 



HOUSEHOI.D CHEMISTRY 233 

tity of 20 per cent. NH^OH (3 volumes ammonia specific 
gravity 0.9 -f- i volume HgO = 20 per cent.). 

Viscogen. — Dissolve two and one-half parts of granu- 
lated sugar in five parts of water. Slake one part of 
lime in three parts of water, strain and add to the sugar 
liquid. Shake frequently for two or three hours and 
allow to stand; finally pour off the clear liquid (viscogen) 
and keep in a well stoppered bottle. Access to air turns 
the liquid dark but does not impair its usefulness. 



APPENDIX. 



Useful Tables and Equivalents. 





Per cent. 


Sp. Gr. 


Degrees Be 


H SO. 


0.935 
9.584 
93.5 (cone.) 

1. 124 
10.17 
20.00 
40.55 

1.2 
10.06 
11.84 
20.59 
24.81 
32.47 


1.007 
1.066 
1.835 

1.006 
1.05 
I. 1027 
1.2033 

1. 014 
1. 116 

1. 134 
I.231 
1.274 
1.357 


J 


HCl 


9 
66 


NaOH 


7 

13.5 
24.5 






15 
17 
27 
31 
38 



I gram 



{■! 



432 grains 

0353 oz. 
0022 lb. 



28.35 grams = i oz. 
453.6 grams = i lb. 
I kilogram = 2,2 lbs. 
I teaspoon = 5 cc. 
I tablespoon = 15 cc. 

I cup = 16 tablespoons 
2 cups = I pint 
I liter = 1.057 qt. (U. S.) 
I inch = 2.54 cm. or 0.0254 meter 
I foot = 30.48 cm. or 0.3048 meter 

Method of changing from a stronger to a weaker solu- 



house;hoi.d chemistry 



235 



tion, e. g., from acetic acid of 50 per cent, strength to 20 
per cent. : 

20 per cent. : 50 per cent. : : 100 cc. : jt cc. 
X = 250 cc. 
Therefore make up 100 cc. of the 50 per cent, acetic 
acid to 250 cc. 

Interchange of Centigrade and Fahrenheit degrees: 



C = -|(F-32). 
Comparison of Fahrenheit and Centigrade degrees: 



F =-2-0+32 



Fahr. 


Cent. 


Fahr. 


Cent. 





-17.78 


95 


35.00 


32 


0.00 


98 


36.67 


40 


4.44 


100 


37.78 


41 


5-00 


104 


40.00 


50 


10.00 


113 


45.00 


59 


15-00 


122 


50.00 


65 


18.33 


140 


60.00 


68 


20.00 


145 


62.78 


72 


22.22 


158 


70.00 


77 


25.00 


167 


75.00 


80 


26.67 


178 


80.00 






212 


100.00 



To convert degrees Baume to specific gravity apply 
the formulas : 

For liquids heavier than water — 

144 —"^Be" ^ specific gravity. 
For liquids lighter than water — 
144 



134 -1- Be 



7-5 = specific gravity. 



16 



List of Apparatus for Students in Household Chemistry. 



Three rings (iron). 
Filter ring. 
Clamps. 
Triangular file. 
Round file. 
Triangles. 
Wire gauze. 
Steel forceps. 
Wing-top. 
Horn spatula. 
Tube brushes — three (as- 
sorted sizes). 
Filter paper. 
Test tube holder. 
Scissors. 

Knife. 

Thermometer. Centigrade 

0°-I20°. 

Glass rod. with platinum 

wire. 
Flat glasses, 4-inch. 
Blue glass. 
Watch crystals — four. 



Microscope slides with cov- 
er glasses — four. 

Test tubes — i doz. 6-inch. 

Test tubes — i doz. 4-inch. 

Hard-glass test tubes ( i in. 
X 6 in.) — two. 

Graduates, 10 cc, 25 cc. 

Porcelain dishes — two 

• (3>^-inch). 

Beakers (Jaikel 1-4). 

Tripod. 

Test tube rack. 

Agate boilers with cover, 
J^-pint. 

4 funnels — 2-inch and 3- 
inch. 

Flasks — one 4 oz. high. 

Flask s — t w o 4-0Z. low 
(wide mouth). 

Flask — one i6-oz. round 

bottom. 

Wash-bottle — i6-oz. 

Wide mouth bottle, 8-oz. 

Water-bath, 5-in. 



INDEX. 



Acetic acid fermentation, i86. 
Acetylene, preparation of, 84, 

86, 87. 
Acrolein, 131, 136. 
Air, aqueous vapor in, 10. 

carbon dioxide in, 7, 10. 

composition of, 7-14. 

density of, 12. 

diffusion of gases in, 13. 

dust in, 12. 

experiments on, 14-16. 

heat capacity of, 14. 

humidity of, 11. 

liquid, 14. 

nitrogen in, 9, 10. 

oxygen in, 8, 9. 

ozone in, 9. 
Albumins, 142, 148-151. 

tests for, 148-150. 
Alcohol, denatured, 76. 

ethyl, experiments with, 78, 

79. 
ethyl, preparation of, T], 78. 
Alcohols, as burning fluids, 76- 

79. 

Alum, in water purification, 37. 

test for, 33, 175. 
Aluminium, alloys of, 54. 

experiments on, 54. 

in utensils, 54. 

preparation of, 52, 53. 

properties of, 53. 



Ammonia, albuminoid, 33-35. 
free, 33-35. 

Analysis, volumetric and gravi- 
metric, 215-228. 

Antiseptics, 196-198. 

Atmosphere and ventilation, 7- 
2.2. 

Aqueous vapor in air, 10. 

B 

Babcock test, 163. 

Baking powder, home-made, 

172. 
Baking powders, 170-175. 

classification of, 171. 

comparative table of, 173. 

experiments on, 174, 175. 

reactions in using, 171, 172. 
Baume hydrometer, 25, 235. 
Beef extracts, 158, 159. 

food value of, 158. 

tests on, 159. 
Biuret test, 149. 
Blau gas, 85. 
Bleaches, 197, 198, 212. 
Bluings, 213, 214. 
Bones, 154. 

Butter, specific tests for, 139. 
Butyric acid fermentation, 139, 
140. 



Calcium, test for, 33. 



List of Apparatus for Students in Household Chemistry. 



Three rings (iron). 
Filter ring. 
Clamps. 
Triangular file. 
Round file. 
Triangles. 
Wire gauze. 
Steel forceps. 
Wing-top. 
Horn spatula. 
Tube brushes — three (as- 
sorted sizes). 
Filter paper. 
Test tube holder. 
Scissors. 
Knife. 
Thermometer. Centigrade 

0°-I20°. 

Glass rod. with platinum 

wire. 
Flat glasses, 4-inch. 
Blue glass. 
Watch crystals — four. 



Microscope slides with cov- 
er glasses — four. 

Test tubes — i doz. 6-inch. 

Test tubes — i doz. 4-inch. 

Hard-glass test tubes ( i in. 
X 6 in.) — two. 

Graduates, 10 cc, 25 cc. 

Porcelain dishes — two 

• (3>4-inch). 

Beakers (Jaikel 1-4). 

Tripod. 

Test tube rack. 

Agate boilers with cover, 
J/2-pint. 

4 funnels — 2-inch and 3- 
inch. 

Flasks — one 4 oz. high. 

Flask s — t w o 4-0Z. low 
(wide mouth). 

Flask — one i6-oz. round 

bottom. 
Wash-bottle — i6-oz. 
Wide mouth bottle, 8-oz. 
Water-bath, 5-in. 



INDEX. 



Acetic acid fermentation, i86. 
Acetylene, preparation of, 84, 

86, 87. 
Acrolein, 131, 136. 
Air, aqueous vapor in, 10. 

carbon dioxide in, 7, 10. 

composition of, 7-14. 

density of, 12. 

diffusion of gases in, 13. 

dust in, 12. 

experiments on, 14-16. 

heat capacity of, 14. 

humidity of, li. 

liquid, 14. 

nitrogen in, 9, 10. 

oxygen in, 8, 9. 

ozone in, 9. 
Albumins, 142, 1 48-1 51. 

tests for, 148-150. 
Alcohol, denatured, 76. 

ethyl, experiments with, 78, 

79- 
ethyl, preparation of, TJ, 78. 
Alcohols, as burning fluids, 76- 

79. 
Alum, in water purification, 37. 

test for, 33, 175. 
Aluminium, alloys of, 54. 

experiments on, 54. 

in utensils, 54. 

preparation of, 52, 53. 

properties of, 53. 



Ammonia, albuminoid, 33-35. 

free, 33-35. 
Analysis, volumetric and gravi- 
metric, 215-228. 
Antiseptics, 196-198. 
Atmosphere and ventilation, 7- 

2.2. 
Aqueous vapor in air, 10. 

B 

Babcock test, 163. 

Baking powder, home-made, 

172. 
Baking powders, 170-175. 

classification of, 171. 

comparative table of, 173. 

experiments on, 174, 175. 

reactions in using, 171, 172. 
Baume hydrometer, 25, 235. 
Beef extracts, 158, 159. 

food value of, 158. 

tests on, 159. 
Biuret test, 149. 
Blau gas, 85. 
Bleaches, 197, 198, 212. 
Bluings, 213, 214. 
Bones, 154. 

Butter, specific tests for, 139. 
Butyric acid fermentation, 139, 
140. 



Calcium, test for, 33. 



238 



INDEX 



Carbohydrates, 88-122. 
celluloses, 116-121. 
classification and occurrence, 

88-91. 
description of, 88. 
dextrin, 114, 115. 
fructose, 100, loi. 
galactose, loi. 

general reactions of, 94, 95. 
glucose, 95-99. 
glycogen, 115, 116. 
hydrolysis of, 92, 93. 
in fruits, 123, 125, 127, 128. 
lactose, 107, 108. 
maltose, 104-106, 
optical activity of, 93, 94. 
photosynthesis of, 91, 92. 
practical work on, 121, 122. 
solubilities of, 94. 
starch, 108-114. 
sucrose, 101-104. 
ultimate composition of, 94, 

95. 
Carbon dioxide determination, 
175. 

in air, 7, 10. 
Carbonates, test for, 33. 
Celluloses, 116-121. 

experiments on, 118-121. 

occurrence of, 116, 117. 

properties of, 117, 118. 
Cereals, 121, 122. 

analysis of, 224-226. 

practical work on, 121, 122. 

Cheese, 168, 169. 



Chlorides, in water, 36. 

test for, 33. 
Chocolate and cocoa, 181, 182, 
Cleaning agents, 201-214. 

classification of, 201. 

tests for, 209, 212. 
Clotting, 146. 
Coagulation, 145. 
Coal, fuel value of, 69. 
Coal gas, 81, 82. 
Coffee, 177-181. 

experiments on, 178. 

notes on making, 178- 181. 
Copper, alloys of, 51. 

experiments on, 52. 

manufacture of, 50, 51. 

properties of, 51. 
Cotton, tests for, 120. 
Cottonseed oil, tests for, 138, 

139. 
Curdling, 146. 

D 

Density of air, 12. 
Dextrin, 114, 115. 

experiments on, 115. 

preparation of, 114. 

properties of, 114. 
Diffusion of gases, in atmos- 
phere, 13. 
Disinfectants, 195-200. 

tests for, 199, 200. 
Disinfection, 195-200. 

chemical methods of, 196-198. 

physical methods of, 195, 196. 
Drying oils, 132, 138. 



INDEX 



239 



Dust, in air, 12. 



Eggs, 148-151, 154-156, 193- 
tests on, 154-156. 

Enamel ware, 63. 

Ethylene, preparation of, 86. 



Fats, 129-140. 
acids in, 130. 
chemical nature of, 129. 
experiments on, 135-139. 
hydrotysis of, 133. 
properties of, 130-135. 

Fatty acids, 130. 

Ferments and preservatives, 

183-194- 
Ferments, 183-187. 
acetic, 186. 
butyric, 186, 187. 
experiments on, 187, 188. 
lactic, 184-186. 
yeast, 183, 184. 

Filters, household, 38. 

Formalin, in milk, 167. 

Flue dust, corrosive action of, 

70. 
Fructose, 100, loi. 
experiments on, 100, loi. 

Fruits and fruit juices, 123-128. 
Fruits, analysis of, 125-128. 

composition of, 123-125. 

in jelly making, 128. 



Fuels, 67-87. 
classification of, 67. 
gaseous, 79-86. 
liquid, 70-79. 
solid, 68-70. 



Galactose, loi. 

Gas, 80-87. 
acetylene, 84, 86, 87. 
analyses of, 82. 
Blau, 85. 
coal, 81, 82. 

combustion of, 83, 84. 
naphtha or gasoline, 84, 85. 
natural, 79, 80. 
Pintsch, 85, 86. 
water, 80, 81. 

Gas meters, 83. 

Gases, fuel and illuminating^ 

79-87. 
Gasoline, tests on, 74, 75. 
Gelatin, 152-154. 
Glass, 62-64. 
GHadin, 152. 
Globulins, 143. 

separation of, 150. 

special tests for, 149, 150. 
Glucose, 95-99. 

experiments on, 97-99. 

preparation of, 95. 

properties of, 96, 97. 

structure, 95. 
Glucosides, 99. 
Glutelins, 152. 
Gluten, 152. 



240 



INDEX 



Glycerides, 129. 
Glycogen, 115, 116. 

H 
Hardness of water, 38-42. 
Humidity in atmosphere, 11. 
Hydrogenation, 132. 
Hj'^drolysis, definition of, 26. 

of carbohydrates, 92, 93, 

of fats, 133. 

of proteins, 146, 147. 



Ice cream, analysis of, 167. 
Indicators, use of, 218, 219. 
Iodine value, of fats, 138. 
Iron, 43-50. 

experiments with, 47. 

in utensils, 44. 

galvanized, 46, 50. 

manufacture of, 43, 45. 

oxides of, 43. 

properties of, 44, 47. 

tests for, 33. 



Jelly making, 128. 

K 

Kerosene, 75, 76. 

L 

Lactic acid fermentation, 184- 

186. 
Lactose, 107, 108. 
Latent heat of water, 2^, 24. 



Lead, 59, 60. 
Lignocellulose, 120. 
Linen, tests for, 120. 
Liquid air, 14. 
Liquid fuels, 70-79. 

M 

Magnesium, test for, s$. 

Maltose, 104-106. 

Metal poHshes, 210-212. 

Metals, 43-61. 

Metaprotein, preparation of, 

150, 151- 
Methane, preparation of, 86. 
Milk, 159-167. 

analysis of, 159, 164, 165. 

average composition of, 159. 

condensed or evaporated, 167. 

detailed composition of, 159- 
161. 

effect on, of heating, 161. 

effect on, of rennin, 162, 165, 
166. 

fermentation of, 162. 

sour, 161. 

souring of, 161, 166. 

tests on, 162-167. 

Muscle, 156-158. 
constituents of, 156, 157. 
experiments on, 157, 158. 

N 
Naphtha gas, 84, 85. 
Natural gas, 79, 80. 
Nickel, 47, 48. 



IND^X 



241 



Nitrites and nitrates, in water, 

35, 36. 
Nitrogen in air, 9, 10. 

O 

Optical activity, 93, 94. 
Organic chemistry, outline of, 
2-6. 

Oxygen consuming power, o£ 
water, 36. 

Oxygen in air, 8, 9. 

Ozone in air, 9. 



Paper, tests on, 120, 121. 
Pectin and pectose, 123, 124, 

128. 
Petroleum, 70-73. 

chemical nature of, 72, 'j'^- 

combustion of, 73, 74. 

cracking of, 71. 

development of industry, 70, 

71. 
distillates from, yi2. 
experiments on products of, 
74-76. 
Photosynthesis, 91, 92. 
Phosphates, test for, 32. 
Pintsch gas, 85, 86. 
Polishes, metal, 210-212. 
Pottery and porcelain, 65, 66. 

Preparation of N/HCl, 216, 
217. 
of N/NaOH, 217, 218. 



Preservation of foods, 188-191. 

chemical methods of, 189, 190. 

physical methods of, 188, 189. 
Preservatives, experiments on, 

190, 191. 
Proteins, 141-169. 

albumin, 148- 151. 

alcohol solubles, 152. 

beef extracts, 158, 159. 

bones, 154. 

cheese, 168, 169. 

classification of, 141, 142. 

description of, 141. 

tg%, 148-151, 154-156. 

gelatin, 152-154. 

globuHn, 151, 152. 

glutelins, 152. 

hydrolysis of, 146, 147. 

in fruits, 124, 127. 

milk, 159-167. 

muscle, 156-158. 

occurrence and solubilities 
of, 142-145. 

properties of, 145-147. 

ultimate composition of, 147, 
148. 
Proteoses and peptones, prepa- 
ration of, 151. 
Purity of foods, tests for, 191- 
194- 

R 

Rancidity, 134. 

Reagents, preparation of, 229- 

233. 
table of, 229. 



242 



INDEX 



Reducing sugars, estimation of, 

2.2'J, 2.2%. 

Rennin, 146, 162, 165, 166. 



Saccharimeter, 102, 103. 
Saccharin, 193. 
Salt-rising bread, 185. 
Scouring powders, 209-211. 
Silver cleaning process, 57. 
Silver, 54-57. 

alloys of, 56. 

in utensils, 57. 

preparation of, 55, 56. 

properties of, 56. 
Soap, analysis of, 206, 209. 

average composition of, 206. 

chemistry of making, 134, 
, 206, 207. 

cleansing action of, 202. 

cold, 206-208. 

manufacture of, 202-205. 

recipes for, 207, 208. 

rosin in, 206. 

tests on, 209. 

Solutions, normal, 215-219. 
Starch, 108-114. 

experiments on, 111-114. 

properties of, 108-111. 
Steel, 45, 46. 

Sucrose, 101-104. 
experiments on, 103, 104. 
properties of, loi, 102. 

Sulphates, test for, 33. 



Tea, 176, 177. 
Tin, 57-59. 

alloys of, 58. 

experiments on, 59. 

in utensils, 58. 

manufacture of, 57, 58. 

properties of, 58. 

U 
Unknown substances, method 
of testing, 219, 220. 



Ventilation, 16-22. 

methods of, 20-22. 

relation of carbon dioxide to, 
18-20. 

relation of heat and humidity 
to, 16-18. 
Viscogen, 104, 233. 
ViteUin, 155. 
Volumetric analysis, 215-228. 

applications of, 220-224. 

W 

Water, 23-42. 

boiling and freezing points 

of, 24, 28. 
chemical properties of, 25-27. 
compressibility and expansion 

of, 25. 
conductivity of, 24, 27. 
density of, 25. 
hard and soft, 38-42. 
latent heat of, 22,, 24. 



INDEX 



243 



Water, mineral matter in, 30, 
of hydration, 26, 29. 
of hydrolysis, 26, 27, 29. 
of solution, 26. 
oxygen consuming power of, 

36. 
physical properties of, 23-25. 
purification of, 37, 38. 
qualitative examination of, 

30-36. 
specific heat of, 24. 
total solids in, 32, ^s. 



Waters, natural, classification 
of, 29, 30. 

Wood, 68, 69. 



Yeast fermentation, 98, 183, 
184. 



Zinc, 48-50. 



» 



f * 

f i 

! Food Industries 1 

I I 

I An Elementary Text-Book on the Production and « 

i Manufacture of Staple Foods I 

f i 

\ BY ! 

^ ' 1 

I HERMANN T. VULTE, Ph. D., F. C.S. | 

: Professor Household Arts, Teachers College, Coliunbia University j 

t AND 4 

I SADIE B. VANDERBILT, B. S. | 

i . i 

f Instructor Household Arts, Teachers College, Columbia University, | 

» New York, N. Y. ♦ 

f i 

? Contents. — Introduction. Chapter I. — Food Princi- 

i pies. Chapter II. — Water. Chapter III. — Cereals. Chap- 

I ter IV. — The King of Cereals. Old Milling Processes. 

t Chapter V.— Modern Milling. Chapter VI.— Breakfast 

\ Foods and Coffee Substitutes. Chapter VII. — Utilization 

I of Flour. Breadmaking. Chapter VIII. — Leavening 

t Agents. Chapter IX. — Starch and Allied Industries. 

I Chapter X.— The Sugar Industry. Chapter XI.— Fruits, 

I Vegetables and Nuts. Chapter XII.— Alcoholic Bever- 

t ages. Chapter XIII. — Alcoholic Beverages (continued). 

I Chapter XIV.— Fats. Chapter XV.— Animal Foods. * 

i Chapter XVI.— The Packing House. Chapter XVII.— | 

t Milk. Chapter XVIII.— Milk Products. Chapter XIX.— | 

• Preservation of Foods. Chapter XX. — The Canning In- * 

\ dustry. Chapter XXI. — Tea, Coffee and Cocoa. Chapter \ 

I XXII. — Spices and Condiments. Bibliography. Index. | 

t k 

I 8vo. Pages X + 327. 81 Illustrations. I 



« 



I Price, $2.00, Postpaid. | 






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